Overall pretty good

Why no desktop cases anymore?:
I'm in the process of building a personal file server.  I was really looking for a desktop (horizontal) case, but nobody seems to make them anymore.  I found some cooler master units I was less than impressed with.  All else seems to be expensive HTPC cases, if they're horizontal.
I finally figured I'd buy a (hopefully sturdy) mid-tower and just lay it down horizontal.  Yes, this means the optical drive is turned 90 degrees, but I can live with that.
After extensive shopping, I kept coming back to the Antec Three Hundred, and a couple of models from NZXT.  From reading reviews, it seemed the Antec Three Hundred was probably the safest bet.  But then, everybody and their brother buys Antec or Cooler Master.  I wanted something different.  So the Source 220 was my choice for my file server.

Unboxing:
I was surprised at how LIGHT the case is.  It's a relatively sturdy case.  By the rigid feel of it, you would expect it to weigh a lot more than it does.  The only thing that makes sense to me is that all the ventilation mods must have removed a *significant* amount of material.  Still, while I didn't weigh this case...it seems to weigh about half as much as you'd expect it to, just by looking at it.  It's finished matte black everywhere, which looks really nice.  Pictures you'll see online really don't do this case justice.  It's sharp looking!

System:
Still a work in progress.  But so far:
Corsair GS600 power supply (quick comment:  AWESOME!)
Biostar TA75M FM1 socket uATX motherboard
Athlon II X4 631 processor
4GB DDR3 1600 Crucial Ballistic Tactical Tracer CL8 RAM (2 X 2GB)
HIS Silence series HD 6570 2GB video card
LG SATA DVD burner
Western Digital 500GB 2.5" SATA hard drive
OCZ Synapse 64GB SSD Cache Drive
-  With a 1TB notebook hard drive to be added later

Building Thoughts:
OK, so it all fits.  I could squeeze an ATX mainboard in there if I really wanted to, but I like the way the micro-ATX board leaves some space between the motherboard and the bottom-mount power supply. 

Power Supply:  You can mount power supply either direction (fan up, or fan down).  I think it makes most sense to leave the fan facing "up" (inside) as it will pull in less dust that way.

Motherboard:  The case includes standoffs (you have to install all of the standoffs yourself).  There is a handy chart IN the case (hidden by the motherboard eventually) that shows where the standoffs should go.  Unfortunately, the chart is wrong.  Ignore the chart, just visually inspect your motherboard to see where the standoffs are needed.

Fans:  The included 140mm and 120mm NZXT fans move a lot of air and do so very quietly.  I'm running them off of the motherboard.  I moved the fans from their original positions though.  As I'm planning to use the system horizontal, I've got the 140mm fan as an intake on the 'top', which is the right side.  I've got the 120mm fan as an intake on the 'bottom', by the power supply...as this is the left side.  NZXT did some pre-wiring at the factory.  This meant I had to cut some cable ties to free the wiring for the fans before I could move them.  Unfortunately, the included fans have molex pass-through connectors on them.  This makes wiring the fans to the motherboard look a little sloppy.

Video card:  I'm using a rather short (length) low-profile video card.  But there's enough room around the video card that ANY video card should fit fine. 

Optical Drive:  I love the way NZXT designed the mount for the optical drives.  They are very sturdy, easy to use (tool-less) and hold optical drives very tightly.  If only they'd done the same for the hard drives...

Hard Drives:  Oh wow, I can't possibly over-emphasize this next sentence:  NZXT screwed up on the hard drive mounting system, big time.  I only have 2.5" hard drives.  But I put them in 3.5" mounting brackets.  So, evaluating the *3.5"* storage drives mounting system in this case, I am really disappointed.  The brackets used (tool-less) have little steel posts that go into the drive (or the drive mount), and the entire assembly is held together by a very thin little plastic tab you twist into position.  This plastic tab is so fragile, it would be very easy to break it under normal use / installing hard drives.  When this tab is "locked", the drive is so wobbly, it hardly feels like it's mounted at all.  I would be afraid to carry this case to a LAN party, because I'd be wondering if my hard drives were going to bounce around the interior of my case!
You can put normal hard drive mounting screws into the "right" side of the drive cage to better support the hard drives.  But if you're going to do that, then why bother with the tool-less mounts?

More on Hard Drives:  While we're on the subject, why are there no 2.5" drive mounts?  SSDs are practically the norm now (all of them are 2.5", that I have seen).  I happen to have extra 2.5" spinning platter drives from various notebook "projects", so why waste them?  It's frustrating to see a current model mid-tower case with no (zero) 2.5" drive mounts!

Wiring:
The wiring from the case is high quality, and plenty long for good cable management.  The labels on the connectors are not as clear as they could be. 
While there is *some* space behind the motherboard to tuck away extra cables, there is not quite enough space.  Some of your cables are going to get a bit squished when you put the "right" cover back on this case.  There's plenty of room behind the hard drive mounts area for extra cables, but that would look messy.
I'd like to see at LEAST another centimeter of space behind the motherboard tray for hiding cables.  Or a hidden compartment just for cables, like the Antec Three Hundred. 

Cooling:
OK, it's hard for me to imagine a case that might possibly have better cooling.  You've got SEVEN fan positions, all supporting 120mm fans!  (some support 140mm fans, as well)  There are two fans included, one 140mm and one 120mm.  That should be enough for an average system.  But if you need a case with superior air cooling, just get this case and a few extra ~120mm fans.  The possible CFM airflow through this thing is incredible!
Because I'm using it horizontal, I've got all the fans pulling air INTO the case, one on top (right), one on bottom (left) and I added an Antec Tricool to the front to blow air across the hard drives.

Interesting side note on cooling:
My Corsair GS600 is designed to run in FANLESS mode until it gets warm.  If I stress test this system to max out power draw for several minutes, I can just start to get the power supply warm enough that the fan starts to twitch.  But the only time I've seen the power supply fan actually run is for a few seconds at each startup.  Yes, the fan works.  In this case, with just three cooling fans...the system stays cool enough that the power supply runs in fanless mode consantly!

On dust:
I'm not happy at all that NZXT doesn't include any fan filters.  The bottom fan position even has brackets for a fan filter, but no fan filter.  You can obviously buy fan filters to add them.  But they really should be included with the case.

System impression:
I'm overall pretty happy with the way the system turned out.  All looks nice and neat.  Cooling is very efficient, with nearly silent fans.  I'd definitely consider buying another NZXT case for my next build!  But I'll pay attention to the hard drive mounting system.  I'm hoping NZXT will be smart enough to fix that problem (and it is a problem).
The frustrating thing is, NZXT could have used the *exact same* mounting system for the hard drives that they used for the optical drives.  The former is terrible, the latter is perfect.  So there's really no excuse for the horrible hard drive mounts in this thing!  All NZXT had to do was add 8 more mounts similar to the optical drive mounts!  Why didn't they?