" I mean using Windows XP ist not really abolutely necessary on a dedicated GS machine, and if you are a professional you must be running GS on a dedicated machine"
I disagree with that. I am foremost a software developer and I know that any piece of software that requires a dedicated machine (save an operating system) is a badly designed piece of software. I myself have attempted to create a hard drive sampler that would replace GS and was successful in getting the tech. to work with Windows XP and DirectX - totally hardware friendly. You could even run other apps while the sampler was running. But I can't actually go the extra mile or sell what I made because of the patent.
And as for limitations, as I said, not only are there frequent crashes both in Windows 98 and XP, but GS hasn't had a single new feature since version 2 (unless you count modest XP support as a feature). That means that while sound technology is booming, such as 3D hardware, digital surround output, etc., Gigastudio doesn't support any of this. Another limitation is the small number of splits you can have. Each instrument can only have a maximum of 32 splits. I designed a sampler system that would have an unlimited number of splits, but again, can't make it because I might get sued. Another limitation is that we're still using an ADSR envelope which does not at all adequately capture the true nature of an instrument. Again, I designed a system that would use a 100% variable envelope. Another thing: COM/Automation support. With that, it would be possible for the user to write macros in GS that would creatively respond to any MIDI message using code as opposed to the limited split functionality. This would eliminate the need for something like the VSL performance tools. And the list goes on and on and on.
So, those are the answers to your questions. I'll end with one other funny thing about Tascam, why I think they're a terrible company. People have been complaining about the Conexant WaveStream error for a long time now and Tascam is unable or unwilling to fix it. Finally, after arguing with the users over whether they could do anything about it, one of the reps actually told a user to let them borrow his computer so they could find the bug. While a couple people actually volunteered for this, most, including myself, were disgusted that a company would actually expect a user to ship them his computer so that they can find a bug in their own software. I told them they should replicate the hardware conditions and do it themselves - no reply to that one.
This is a Mickey Mouse company who has no business owning the patent on hard drive sampling technology. They don't know how to handle this product, and as a result, it's in the stagnant buggy state it's in. Tascam's only response is yours; use a dedicated machine. I find that unacceptable.
At any rate, there's really no point in arguing Tascam's merits any further. The VSL guys know my complaints about GS and are obviously considering what the best platform for VSL will be. I really hope it sparks something new and wonderful.