Are there any advantages in SQL Server Always On vs. SQL Server 2008 R2 Mirroring with only two nodes? We are currently hosting a SaaS website on two Windows 2008 R2 / SQL Server 2008 R2 Servers. Would upgrading to SQL Server 2012 / Always On give us any advantages with respects to high availability?

Note that while we are looking for high availability, high performance is not really an issue for us at the moment, so being able to run read-only queries on backup database servers is not really important.
Readable Secondaries: you can query the 'mirror'. See AlwaysOn: High-Availability and reads Scale-Out.