I think it looks kind of tacky personally. I just have a table near the cab where the drinks can go down...besides if you are playing with one or more buddies there is plenty of time to get a sip in between your player ups.
+1 for the side tables
I guess if the cup holders more or less disappeared from site completely when they closed up, they'd be alright.
The sight of cabs with cupholders screwed to the sides though, for me, just seems a bit too, "I couldn't be bothered to think of anything nicer so what the hell". I guess if it was going in a game room with neon signs on the walls, or some similar bar-esque theme , it'd work ok.
Why not pop out holders on the sides of a control panel, like you seen in the dash boards of many new cars these days? Heck, why not rip one from a late model wreck at the scrapyard to build into a cab. THAT could be cool!