Let's say this first and get it out of the way:
This is a *BASIC* controller, and is not aimed at people looking for precision gaming - and it will most probably *NOT* work straight out of the box for most games. So if you're the kind of person who doesn't want to download keyboard mappers, this is probably not for you.
Having said that, this is really an excellent basic controller, because it needs no installation disk, and is completely plug-and-play (at least it is on Vista).
Being in the familiar Playstation controller shape, it is quite comfortable to hold, and the build feels quite sturdy.
For real gaming, as mentioned earlier, this will most likely not work directly on a lot of games (for instance it worked on NFS Underground2, but not GRID) so in these cases you will have to download and use a mapper software to map the keyboard onto the buttons - so your game still thinks you're using the keyboard while you're on the pad.
There's plenty of good mappers like JoyToKey, Xmapper etc. that should work.
The analog stick, in my opinion, works pretty much like the d-pad; I didn't really see any "analog" precision, but then for this price I didn't really expect much.
I would say this controller is aimed at people like me;
someone who doesn't play a lot of games (that would justify buying an expensive controller) and only needs a basic controller, just to keep the laptop keyboard from getting ruined - AND doesn't mind downloading mappers and tweaking around with it.
Bottom line:
If the above describes you - go for it, you can't go wrong.
But if you need more, this is not the one for you.