1. Any good bars/clubs to catch some live music nearby?
There are lots of music venues here, but they can be hit or miss depending on who is playing and what your musical interests are. The only one I can think of that is walkable from the GWCC is the Tabernacle. It's a super-cool venue, but again, it depends on who is playing. Other places that I can think of off the top of my head who book decent bands: Fox Theater, Variety Playhouse, Masquerade, the Earl, and Vinyl/Center Stage.
2. Any cool Guitar shops around that I can spend some time noodling on a guitar after-hours?
Maple Street Guitars has an amazing acoustic selection. Boutique Guitar Exchange has a nice selection of electrics and amps, as does Atlanta Discount Music. As much as I hate the company, I will admit that the Guitar Center off of Druid Hills has an impressive inventory...it's the flagship Guitar Center in Atlanta, and they have a "showcase" room that is only open at certain times where they stock custom shop Fenders, custom shop PRS's a few $20k vintage guitars, etc..
3. Anything that I've 'just gotta see' while I'm there?
Check out the Georgia Aquarium. I think it's the largest aquarium in the world....really, really impressive (whale sharks and belugas!), and is walking distance from the GWCC. The CNN tour is right down there as well, and is pretty interesting. The World of Coke tour is close, but I'd probably skip that. The Taco Mac bar in CNN Center has a great beer selection if you get thirsty.
