Ok so I found some time to do a few tests, the software i have used is CrystalDiskMark on a Windows 2008 R2 VM, running on a IBM x3650 M4 Server (791552G) with stock IBM SSDs, 1 VM per SSD, ESXi version is 5.1 build 799733.
Based on the results there is no difference in the performace, at least under Windows (see attached file). Maybe there is something i'm missing, but in my opinion there is nothing to be gained from tagging the drive as a SSD, besides being able to use it as the host cache of course. Even the smart metrics are not being passed on to ESXi, so there is no convenient way to monitor the drives health. Meh.
