I personally love mine, but it is a very love/hate design.
It's very substantial in hand (which is short-hand for it being thick, heavy, and possibly awkward depending on your hand/finger size). Opens smooth and locks up tight. I haven't had a problem with the thumbstuds, but many have.
The only problem I have with it, and it's a very common complaint, is the pocket clip. It's almost impossible to carry without destroying your pants...that is, if you can get it clipped in the first place. I can't honestly say removing the clip improves the situation, because it's rather big to be carried in-pocket.
I'd second getting one in hand before buying it. I didn't, so I was lucky that I liked it. Many others haven't been so lucky, as evidenced by all the sales on the Exchange.