To tag onto Ryszard's comments:

My reason for wanting true and deep VST/VSTi integration is actually the exact same reason as Ryszard's desire for ReWire:

Choice of instrumentation and sound sources.

Ryszard's decision was to learn Reason deeply and the way forward for integration is through ReWire; which has become somewhat standard fare for DAWs, even the others that are under $100 like Mixcraft, nTrack, etc.

My decision was to look for VSTi that did what I needed them to do; Jamstix for being my drummer, all of the GSi physically modeled old-school electromechanical keyboards.

I also got hooked on tempo-locking effects like Kjaerhus' autofilter, any number of delay plugins, etc.

I wasn't happy with Sound Canvas or even soundfont playback.

Lots of forumites here made this into a hardware decision - buying the Ketron GM module, but those of us that have wandered outside the world of GM are those that point to these features as necessary.

What did it for me was trying the CMuzys freeware DAW that came on the cover CD of computer music magazine. That had great ASIO integration, and allowed playthrough of VSTi. The first time I fired up the Minimogue VSTi (freebie), I spent many long nights playing old prog-rock synth leads - or at least trying. Something I hadn't been able to do for 20 years! I was hooked.

-Scott