I bought a V1 model off Cadder when I first got my PS3 as I had a lot of trouble aiming with thumbsticks.
They're ok, my biggest problem was that the mouse buttons don't work very well, they function more like a controller button that you have to press rather than a mouse button you just click (if that makes any sense). It basically means half the time you press it nothing will happen, or there will be quite a delay. I ended up pulling it apart and sticking in some extra contacts and such so it would work properly.
It also has problems with games that have acceleration in the aiming, like Killzone 2 and Far Cry 2. When you use a mouse with a PC game there usually isn't much acceleration as the aiming speed is simply how fast you move the mouse but console games have this acceleration due to the limitations of thumbsticks. So you'll turn to aim at something only to find you've turned too far because the acceleration has kicked in. Even more noticeable when making fine movements like sniping and such.
Not sure if they fixed these issues in V2, though I hear it's a lot jumpier making fine aiming much more difficult.
I found it was good for the CoD games, but because it didn't work too well with my other shooters I ended up getting used to aiming with a controller anyway.