Pros: tiny; good battery life; Rockboxable
Cons: tiny letters, don't love the native UI
Rockbox it and you've got great sound in a tiny package. Give it to an amp and it's better yet, but not so portable.
After looking around at some other reviews, here are a few more details. First off, I should say that I'm a music lover, not an audiophile (yet). Although I can detect some differences - between amped and unamped sources, between the different headphones and IEMs I own for example - I don't yet have the depth of experience or language to give an extremely detailed review of this little player.
Did I say it was little? We're talking 2" x 1" here. It would be hard to get more portable. Unmodded, it's perfectly reasonable and extremely cheap. However, if you get it, you should Rockbox it for the amount of control (database, EQ, and a lot more that I haven't fully explored) you get.
What makes this stand out for me is the fullness of the sound. I don't demand overwhelming bass and the Clip+ provides more than enough for me. The midrange is forward and detailed, as are the highs.
For the price, I think it's hard to get a better small player.