I own this stereo for more than 4 years, and must say that sound o fit surprised me more than once. With compact design and it's 22 W per channel power it is all you need for home stereo for music listening.

Sound quality

Sound quality is the most impressive thing about this stereo. It comparable with top Yamaha Piano Craft stereo systems (while being noticeably cheaper), and much better than many devices in this price range. When I was buying this unit I tried out many other devices, and only mentioned Yamaha had a better sound. Onkyo, Sony, other Denon units where left in dust behind with its dull and shallow sound.
Let's start from the bottom - bass is powerful, yet not overwhelming. For some people it is a bit to strong, but it can be easily helped by changing devices settings. While listening to organ works by Bach it goes all the way down without a problem and never shows any distortion. Middle and high tones are nice and crisp - no problem with resolution, you can hear different instruments playing. Sound is nice, juicy and warm, though you should watch placement of speakers closely - if they are too close together, or if you are sitting not in front of them it worsens sound noticeably (like in any stereo system). Also it should be noted, that unit have to play for 3-5 minutes to reach it's best. I hardy notice this, since it plays most time in my case (first thing I do when coming back to my place is to turn stereo on), but it is important when you want to test it.

When listening to music very silently dynamics suffers a little, but it isn't big issue - it is hardly noticeable.
It should be noted that sound greatly depends on speakers - in my case unit came with 60W Denon speakers with bass reflex. Can;t write too much about them, because I never tried any other speakers. The only thing I changed was a speaker cord - but that helped very little, showing that original cord is quite good.

In last words I will warn any of you against Denon M30 and M33 units - one being earlier version of presented stereo, other being newest. Listened to both of them and sound quality was noticeably poorer. Seems that M31 is exceptionally well done.

Tuner, CD, line-in

Tuner works fine, though it has some trouble with week signal. I', going to buy big outdoor antenna soon in hope that it will fix the problem. Other than that it is quite OK. Sound is very good for a radio, being comparable with stand alone tuner units that cos about as much as this whole system. (I can't say it has as good sound, but difference isn't that big). Never tried to listen to anything other than FM radios, so can't say anything about AM quality.
CD is very good - reads most CD without a problem, but i recall some trouble with CD-RW's. Sound is excellent. However mine unit after some time (2-3 years) started to be noisy with some CD's. In most cases it is enough to open and close CD, but sometimes mechanical noise cannot be helped. In this cases if you are listening to music not loudly it is irritating. I have a feeling, that issue depends on quality of CD's, and hope it can be mended - it didn't use to do that.
There are two sets of In and Out cinch connectors. I usually connect my PC to one of them and it is good for that. However if you want to connect phono you will need preamplifier. This is understandable since few people today listen to music using phono and inbuilt preamp would increase price. Other than that there are no limitations and you can easily connect any brand of tape deck, MD drive, or other audio device.

Other features

Among minor features there is possibility to set timer ON and OFF, sleep feature, bass / treble correction, clock and remote. Remote is quite good, allowing to access most features (including features of M31 series MD drive and tape deck). The little annoying is fact, that display on unit cannot be dimmed.
I also have a feeling that CD supports HDCD technology increasing quality of sound (I have two Van Halen CDs with this technology and they sound really great), but never found it in operating manual.

All in all

I think this is the best stereo for this money. The biggest problem for me is lack of tape deck, but few people will miss that ;). If you know you want to listen to tapes there are two choices - either you will buy external unit or you can look for a bit more pricey other compact stereo system. But it might be impossible to find one with as good sound quality as this one. If you add some 100$ you can buy Yamaha with better sound quality, but still it is 100$ more expansive.
Also heard people being concerned that 44 W isn't enough, but to be honest I never listened to mine at more than 2/3 of its maximum power (it was very loud). And my room is about 20 m2.
And last thing - I paid for mine about 400-500$ (can't remember exactly how much since I was paying in Polish zloty. For those who are familiar with Poland - it cost 1800) PLN.

Recommended:
Yes