I did it with a 105 triple crankset and it works fine, just like Velo Dog says. I did it because my left shifter failed and I replaced it with a 105 double (didn't know they made one of those, but that's what I bought on Ebay). I figured that if I could only use two chainrings, might as well lose the small one. The only decision you have to make is whether to keep the spacer or not. The spacer makes the center ring the default ring--i.e., the one you spend most time on. If you want to spend most of your time on the big ring, just remove the spacer from the shaft. Shimano explains this very well in their crank assembly instructions. I'm sure other companies do as well.

Personally, I left the spacer in. I use the center (now small) ring for most of my work, shifting to the big ring only at the top end when I want some extra uuummmpf.