Traffic is really terrible in Atlanta. I live in Buford (about 30 miles outside of the city), which is pretty far out (most people in the city think I live in the sticks). I drive to the Buckhead area for work, which is kinda insane. 45 to 60 min. is the norm fo me.
I wouldn't say Atlanta is necessarily bike friendly. Drivers here are pretty aggressive. However, if your used to handeling yourself on a bike in traffic situations, I think you'd be OK.
They are trying to promote alternative commuting methods now, so hopefully they will increase the number of bike lanes, and paths in the city. As far mountain bike paths, there are some outside the city. There are 2 good ones are really close to my house. And of course there are plenty in north Georgia.
All in all Atlanta is pretty cool. If you like jazz, go to Dante's Down the Hatch. Piedmont park is pretty good. There are plenty of venues for music of all kinds. The weather here is awesome. Especially right now. Winters are relatively warm and brief, but the summers can be hot (hey, it is Georgia after all). Air quality can be bad sometimes between the pollution and the pollen.
That's pretty much all the basics.
Good Luck