I used to wear Lululemon as workout wear, and not gonna lie, it was really comfy. And YES it makes anyone's (or almost anyone's) butt look pretty darn good.
My problem is: They don't really have a great sizing system for leg lengths... EVERTHING (pant-wise) is waaay too long for me, so I always had to get them altered. It doesn't seem to matter what size you go with, either... all I have to say is, not every size 10 has 3 foot legs... some of us just have more hip.