I'm also in the Atlanta area, bought Sirius earlier this summer for some of the same reasons as you.
I love it. I chose Sirius over XM for two reasons. Sirius has more Canadian programming/channels, including CBC. Secondly, XM is either part-owned by and/or part programmed by Clear Channel. No way in hell I'm sending a dime of my money to that company. And no, I never have worked for them, it's not sour grapes. I just don't like what they've done to radio, how they do business or how they treat people. Free enterprise. I like that the playlists on the more mainstream channels are just a little deeper than what you get on broadcast radio, without being so deep that you're listening to a bunch of "what was that" songs. Of course, if you like the odd/obscure stuff, they have channels for that. I also like that I am never more than 4 minutes away from local traffic/weather. That's the next best thing to having a local 24/7 all news radio station.
What I don't like: the audio quality. XM is the same, so this isn't a rip on just Sirius. As I understand it, you're basically listening to MP3 audio. So like MP3, sometimes it sounds pretty good. Sometimes it sounds absolutely terrible, to the point I change the channel. Most of the time it's mediocre. Terrestial radio wins when it comes to audio quality.
Other than getting the news from WSB-750, I doubt I've listened to 5 minutes of local Atlanta radio since June. And I used to listen to a few hours a day. Except for WSB-750, broadcast radio in this market is totally irrelevant...and they, the corporate owners and bean counters, did it to themselves. RIP.