A few more notes, this time from the SQL Deep Dive Session
Why you should use SQL AlwaysOn...
...If you have deep pockets :). Note the requirement for Enterprise Edition for AlwaysOn AG. You can do a two node AlwaysOn Clustering Instance with Standard Edition. This is probably where most people will end up going if they don't want to stick with Mirroring.
SQL In-Place Upgrade
When configuring SfB with AlwaysOn you will need to build the DBs on the first node before you configure AlwaysOn on the SQL side. Type the listener FQDN on the first box and the first node FQDN on the last one. After topology creates the DBs you can configure AlwaysOn in SQL and after that's all done you can come back to the topology, edit it and change the last box to the listener FQDN.
Main issues found with SQL AlwaysOn and SfB.