The good news is you can keep your old plan if you want to. The new data plans come in two varieties: $15/month for 200 MB, and $25/month for 2 GB.
The big news is that tethering will finally be available for $20/month. The overage fees will be much more reasonable as well. Most people will rush to complain about no longer having unlimited data plans, but the entire thing seems reasonable and offers people two monthly options.
I would’ve prefered AT&T to offer something like $10/month for 1GB, $20/month for 2GB, $30/month for 3GB, etc.