I probably made a wrong decision. After many years being a Giga user, few months ago I started to use Kontakt 2 on Mac. One main problem:
I can convert my old Giga files to Kontakt files, but the key-switch does not work. If I hit a key, it just plays both layers. There is no way to switch between different layers. Though I can save key-switch .gig to several files while importing them (on the "OPTION> IMPORT"), it's not easy to use.
BTW, I found even without any filter or FX, EQ, the same sample sound differently on Kontakt and Giga Studio. Giga Studio seems to sound slightly better.