Pool bar is my favorite part of Disney vacation, we've stayed at and utilized pool bars at POR, BC, WL, Poly, Swan, CSR, OKW and CB. For the most part I've never had a bad drink at a pool bar (2 exceptions) I've always found the pours pretty generous and the bartenders friendly.
Worst in my experience was OKW, it may have been a bad weekend, or bad timing, but the bar was criminally understaffed, we waited a really long time with the line never moving and ended up just buying vodka in the hotel store and taking it back to the room (it was the only trip we didn't pack our own, of course) I've heard good things, but we were sorely disappointed.
Similar experience at Poly (but we DID get drinks!), but we were there in the summer, and I think they now have a wrist band policy that probably cuts down on the crowd. Also, there was very little shade, not a lot of places to park yourself and waste an afternoon.
Swan- weakest pours. Long Island Ice Tea was more Arnold Palmer.
CBR I remember nothing about. . .so it was probably the best, pour-wise.
CB- Bartender was really nice, but put club soda in my vodka tonic. That's always the FIRST thing I think of when it gets brought up, fair or not.
This brings us to the Top 3 IMH(and boozy)O
#3- Stormalong Bay at Beach Club- scenery is awesome, lots of shade, one of the bartenders didn't know what a Grateful Dead was, but put together a decent one after I remembered what was in it, the availability of solid food allows you to REALLY waste some time.
#2- Muddy Waters at POR- My first Disney Pool bar makes me all nostalgic, so this might be more about that, but it's kinda quiet, the bartenders are super-great, and its again, shady, easy to miss a dinner ADR because you just don't wanna get up and go back to the room
Drumroll-
#1 Trout Pass at Wilderness Lodge- Plenty of covered seating, great pours, great bartenders if you are seated AT the bar, (I still have a handful of swizzle sticks from the bartender after I was asking my sister if having 3 sticks as evidence was "lushy". You probably had to be there.) if not, there's tables close to the geyser, you've got pool, you've got geyser, you've got resort scenery and have never been given club soda in your vodka tonic, that's vacation.