Pure SSD here. 512GB main and an older 128GB (which is completely empty currently). I do have a 1TB mech in there, but just for huge files - stuff from my camera, Fraps videos etc.
All my storage disks are in an HP micro server which is then backed up to an external 4TB and also to CrashPlan.
Couldn't go back to mechanical for anything now. I used to have Windows and my main programs on my 128GB and Documents etc. pointing to a mechanical drive, but moving to pure SSD really does improve performance even further.