I have been in the market for new kneepads for a while now, hoping to get a set that really protect my kneecaps. One of the most prolonged injuries I've had has been bruised kneecaps. Possibly bursitis, I don't really know. It hasn't been particularly bad in terms of regular life activities, but it has greatly affected my ability to work from inside my opponents' guard, turtle, etc. I began BJJ with some regular oversized white padded vollyball pads, but after 6 months the padding began to break up and shift around. For the past year I've used Mizuno pads (quite similar to THESE), but a year and change later I found the need to replace them too, as the padding was on the decline and no longer protecting my patellas.
I picked up a pair of Brute Exo pads in blue. They were very pricey at $16.99 a piece plus shipping, but hey it's protective gear! Anything that helps my knees is worth the premium price. These are wrestling pads and thus you need to take into account the issue of knee mobility -- ability to triangle, if they affect your half guard escapes, etc.
Firstly, the quality is very nice. These are some fairly heavy duty pads. There is a center circle of injection molding that protects against impact, especially when shooting doubles. There are also some smaller molded areas around the center. Stitching looks good; I don't anticipate having any problems with quality. The pads are lightweight and extremely comfortable. I barely even notice they're on, although I have yet to try them out in no-gi.
The back has mesh which allows your knees to breath and subsequently prevents excessive moisture build-up. I assume that this will work in favor of the life of the pad, as less sweat build-up can only be good. And then there's the lack of slippage, which is obviously very important. I am ~145lbs, 5'10" and I purchased a small. They fit perfectly, don't slide around, and I don't think I've had to adjust them AT ALL while rolling. I've had no issues triangling my legs, so chokes and body-locks are no problem. I have yet to be in someone's VERY tight half guard, but as of now I anticipate no problems there, either.
Overall these were a great buy. Despite the overall cost of approximately $40 including shipping, you just can't put a price on gear that saves your body parts. www.budovideos.com carries them for $14.95, but they only have black. For a better color selection (for the extra couple dollars, of course), check out www.eastbay.com. They are a great site with fast shipping.
FOLLOW UP, 7/15/12:
I keep forgetting to reply with a follow up, so here it is before I forget: these are great. I use them every class and I haven't had bruising on my knees. Well worth the price and highly recommended. There is NO issue of working half guard, triangles, or anything. They stay in place and do not inhibit mobility in any way. They are staying in pretty damn good shape, even after X number of washes. I expect them to last over 2 years with no problems, maybe even longer.