Another question: Does Windows Azure SQL Database (aka SQL Azure) run with or without the optimizer hotfix traceflag (4199) from normal SQL Server?
Answer: It currently does NOT run with 4199 enabled.
In the future, we may be able to expose something more specific and advanced here. Customers needing to have this level of control can use SQL Server 2012 in a Virtual Machine instead on Windows Azure. FWIW, we have not seen this to be a significant issue on SQL Azure so far (in terms of escalated support cases). Obviously this can change in the future.