I think I made a final decision
About to buy 2x VelociRaptor 300GB, stripe them (RAID-0), install OS and all programs onto this boot partition (600GB is more than enough for all apps I have), and backup it regularly onto 3TB (4x1TB) RAID-5, single GPT volume. Data, music, videos, databases, VMware images, backups, etc., will stay there.
2x VelociRaptor 300GB is about the same price as 1x OCZ Vertex Turbo 120GB, but I cannot fit all programs I need on 120GB SSD.
What do you think?