I was lucky and I got the 500 local min for $15 a mon or something like that. As far as taxes I don't think its more than a couple bucks here in MI.
Quality of service is overall Good - very good... if you are talking about sound quality that is.
The only problems I've had have been:
1. If you do alot of uploading (like on Bit torrent or other P2P) it can mess stuff up... I've got comcast, and I think I get like 32Kbs upload, and if I have a program (lets say BT) using about 20 of that on any consistant basis, it interferes with call quality
2. Getting the damn box to play nice with my home network... can take quite a bit of fenagling, It's pretty picky (at least the motorolla one I have is) about where it falls on the network chain. but with some effort it works fine. I would suggest buying your own Box, I think Netgear or Dlink makes one, it might be a little better/easier
If this helps, PM me for a refferal link...