I've got one of those exo terras. I like the front opening doors and I find the foam background attractive. Most of the problems you'll find keeping ball pythons in it are just general problems you get with keeping snakes in glass tanks. Depending on your area humidity can be a problem and you may want to cover part if not all of the top screen. Generally I'd suggest checking out the setting up a glass tank thread. If you get a baby you'll want to put a lot of decorations or crumpled newspaper or something to crowd it up so they feel secure. Also a problem I've ran into with them (though for me its not that big of a deal) is my baby ball python crawling behind the foam background. At first I was afraid he'd be stuck and would tear apart the tank to get him out but I've since seen him get back there and back out. I figure eventually he'll be too big to fit underneath it.
(edit) Also while you may be nervous to pick up a snake off of craigslist you may want to comb it for cheap tables, desks, or other furniture to fit the large cage on. I've got mine on a big writing desk.