I'm a little late to the party.
The above mentioned CRYE with removable pads are awesome. I got two pair to T&E in 2010. If they were mulitcam instead of UCP, I'd still be rocking them.
The PX special ALTAs aren't bad either for a low cost reasonable quality set. Mine last a tour in Iraq and ASTAN. They might have saved my knee from a needle in Iraq. (Protip, always look before you kneel).
Most of the other pads the Army issued me are crap.
Also, remember to put your name on your pads. I had a SGT accidentally borrow mine for half a field problem.