Southbends are good machines. Very capable, and as stated, one of the more common "real" lathes in home use. Just like our GT's, use/abuse and upkeep are critical for an older machine.
Biggest issues to look for are broken gear teeth, wear on the bed, wear/vibration on the main shaft bearings, wear/slop in the main screws. There are some tests you can perform to check for wear that aren't too difficult. One involves turning down a round rod about 12-18 inches long and looking for uniform od cut. Can also use a dial gauge to check for run-out. If you look around you can find detailed instructions on checking lathe condition on a perspective purchase.
Best bet is to go to one of the home machinist forums and look around there for more info. Practical Machinist, Home Shop Machinist, Machinist Web are all popular forums that can give you lots of info.
MOST of the time, a good machinist can work around many types of wear in a machine, but it increases the learning curve. There are several good videos out there on teaching you to use a lathe. AGI sells a great (but $$$) series of videos on using a lathe. Several good free series on youtube as well - couple good ones are from Open Source Machine Tools, or a guy named mrpete222 (also known as tubalcain) - lots more but those authors are easy to understand...
A lot of times, what comes WITH the machine (just like a gt) is more of a deal maker/breaker - accessories/tooling are expensive and add up quickly, so if you have to buy separately, consider that. I have often heard it said that you can easily spend as much on tooling as you do on the original machine
The 8-10 inch lathes are good home use machines - they will do most of what you need and have way more capacity than the 7x14 mini lathes also commonly used. And if you get much bigger, tooling/ownership costs go up QUICKLY! They are small enough that they can be moved "relatively easily" (my 16" Hendey weighs 4000+ lbs!). ANY lathe can hurt you QUICKLY, so learn safe operating practices!
Hope that helps.....