MARTA is supposed to build a fair bit of Light Rail here, someday, to connect with the "heavy rail" that exists. The cost of HR apparently is prohibitive, though they may build a few more miles if Gwinnett county ever joins. The baseball park moved to Cobb county which has no MARTA, there is an express bus from near us out to the park (which is one of the worst traffic areas in town). Light rail of course is slower and takes it's power from overhead, while heavy rail takes power from a line near the tracks. Those cars can go 70 mph I'm told, but I've been parallel to one while driving and the go more like 45-50.
I like the concept of express buses that move on grade separated bridges out of urban areas but still can travel on regular streets. The buses here all use NG so they are relatively clean, but I see a lot of them go by empty, or with one person riding midday.
One problem we have is that GA has small counties, 159 of them, and they are relatively independent. So, the Atlanta metro area encompasses 15-20 counties depending on who is counting, each with its own county government and operations, it's very inefficient. MARTA someday is supposed to morph into the ATL which at least will cover all the counties, but not with rail, just buses mostly. Americans don't much like buses it seems, though the hypercheap intercity buses are fairly popular, because they are cheap.
I'm seeing a lot of development, finally, around MARTA stations in town, residential and office, simply because of proximity to the stations. I live in a part of town with cranes everywhere. It seems to me these things "pay off" eventually as a spur to construction and more taxes. The same is true with the Beltline, which is just walking/biking trails today, though SOMEDAY it is supposed to be light rail also, at least in part.