I myself do have to admit that it seems to me most of the focus on Linux
audio to be on recording bands and/or external hardware, and very little
on the modern one-man studio. That's where things like the NI plug-ins
shine.
As an aside, the one Windows VST plug-in to come out recently that has
me completely blown away is one called Olga:
http://www.stillwellaudio.com/?page_id=37
It was written by one guy (with one other person doing the artwork), and
demonstrates the value of modeling the non-linear aspects (saturation
and distortion) of circuits. Check out the "When the TV Breaks" demo
song, if you'd like.
I'd like to pursue creating a single, really sweet soft-synth for Linux,
but long-time posters to this list know my propensity for creating
vaporware (I have a difficult time finishing projects I start), so I
don't want to say too much. I'll just say I've been researching ways to
emulate the non-linear characteristics of circuits and leave it at that
for now.
-- Darren