I use a POD (and a J-Station) all the time. While there are many purists who say the POD ain't as good as a Twin, Marshall, etc - I think it is an excellant recording tool.
In a mix, I or most people who's ears I trust can rarely can tell a POD track from an amp track. Many guitarist who have used my studio (and spent some time with the POD) have been truly impressed with how the sounds meet thier expectations compared to amps being modeled.
Most importantly (or at least to me most relevent) I can record guitar tracks, direct at any time (can't do that with an amp/cab).
I rarely fire up the Fender, Marshall, Peavey or Roland amps sitting in my project studio.
Keep in mind guitar is not my "main axe" I am a drummer, keyboard player (with decent guitar chops). Perhaps if guitar was my main axe I would feel different (but I doubt it).