I'm hoping I like them enough to run on my MTBs as well. I have knee issues here and there too, but mine are all from running. I weigh 175lbs and despite logging over 1,000 miles in the last two years, I still have the gait/stride of a fucking caveman. I've worked with the local running shops and trainers and know what I need to work on, but I'm still usually pretty sore after a 10k.
Lesson learned: Running blows, just ride your bike instead. The problem is that it's really the fuckin' fat destroyer, and a necessary evil if you want to have an extra cheat day here and there full of delicious burritos and summer ice cream cones.