Update: Just tested it and it looks like CM9 Alpha 0.6 (built from ICS 4.0.3) bluetooth tethering isn't working just yet. It pairs just fine, has an option to use the n900 for Internet access, and even has the familiar shaded bluetooth icon from the Honeycomb days indicating tethering is on, but it doesn't seem to be resolving websites.

When I get some time, I'll try to see if I can get to anything by IP to find out if it's just a DNS setup issue of if the routing is broken completely.