Pros: Fairly versatile, sounds good, inexpensive for the quality.
Cons: Heavy, big, awkward to move. Very directional sound.
Speaker cabinets are wonderful because they project sound and a lot of it. The problem for many is finding one that sounds good.
For the sake of running the numbers, let me ask you 'What makes a good cabinet?' My response is then four 12" Sheffield 1200 speakers built to run at 300 W RMS with a 16 ohm resistance input that can use either 1/4" plugs or XLR cables. Set up in a slant design (so that the two top speakers are angled slightly upward while the two bottom speakers are set horizontally), it has dimensions 32.4" H x 30" W x 14.2" D. If you put all of that together you will make a good, though heavy (90 lbs), speaker cabinet.
I think the end result in great because it seems very sturdy. Without a truck, I'm stuck loading this cab into my mini-van for gigs and shows, which leaves me sliding it across two plastic tracks where the seats go in and out. This is obviously not good for the tolex, but so far there isn't even a mark on it. I have dropped one side of this cabinet once, but nothing came loose and it still sounds exactly as it did before.
But the real answer to that question doesn't really deal with construction. A guitarist will probably play through just about anything, regardless of construction, as long as it meets his criteria for sound. After all, sound is where the money comes from!
So how does it sound? For heavy metal, heavy rock, and many other varieties of rock, pretty darn good! For rock and roll, rock-a-billy, and blues, it sounds decent. It provides a nice sound for crunch and for singing lead guitar, allowing some characteristics of the amplifier to shine through, while at the same time preserving its own sound.
What does that mean for the musician? It retains certain effects on the sound regardless of amp. For example, it won't really have a huge thumping bottom end, but it does get plenty dark and has enough thump to be threatening. It also has a comfortable mid range voice that allows a little crunch to shine through in the mid-heavy British tradition. Its highs are nice - not shimmery, but you can dial in a little bit of chime if you use the right amp. Its highs also have the potential for becoming ice-picks in the ears, but I believe that in determined more by the amp.
However, it also lets characteristics of the amp come through. When using my 5150 guitar head, it really let my amp push some seriously distorted tones. By keeping the treble and presence under control on the amp side of things, my high solos retained a warm quality to them. However, I was able to morph my sound completely from happy rock to dark and heavy metal with a change of a couple knobs on the amp.
When using my Orange Tiny Terror, I can pull a wonderful sound through this cab, getting tones ranging from AC/DC, Counting Crows, Jimi Hendrix, and SRV. Of course, it didn't copy any one perfectly, but that it could move toward each sound enough for an audience to know what I was shooting for it a testimony to the versatility of the cab.
A note on projection of sound: As with all closed back cabinets, the 5150 projects sound very directionally. It will shoot at what you point it at, but not a whole lot else. The sound will spread out as it gets away from the amp, so most of the audience will hear it just fine - just don't expect to hear it perfectly yourself while you're on stage (unless you are playing on a very big stage!).
The Rest of the Story
That being said, the first part about the speakers retaining their own character must be remembered. This is not a transparent cabinet, which is why I absolutely do not recommend it if you plan to play jazz or are a super serious blues guitarist, or really any other genre which demands and values clean tones over distorted tones.
For the distorted crowd, the only caveats I have are these: It will not provide the biggest bottom. It will not shine the brightest top. It will not boost the biggest middle. This cab sits in its range very comfortably, but it doesn't go out of it very much. It will cover what ever you throw at it, and it will do it well, but not perfectly.
Essentially, what you get is a heavy, sturdy, rock biased but sonically versatile speaker cabinet. And at around $700, new, it isn't a bad value. The greatest thing about the 5150 in that regard, though, is that it now ebays for around $300 to $500. If you find a deal like I did and nab one for $350, then it is a truly terrific value!