I had the same experience as you with BES 5.0.0 - no issues. I've thought about using CNAME entries for the database mirroring piece in order to avoid any sort of backend server name issues, but I haven't looked at it too much (this is what we do for some of our mirroring configurations). FWIW, as of 5.0.1, they also mention that you must have SQL 2005 Enterprise, although Standard works just fine. I think they have a lot of issues with their documentation (although it's gotten better, which is the scary thing). At least they finally corrected the 'SQL 2003' mistakes from the 5.0 documentation