linux has really come a long way in this department
too many apps to name, many very usable and all can be piped together using a virtual jack server
and an effects server
i think once you get the hang of it like all things Linux it is way more powerfull that using winblows but takes time to learn and some effort to settup/understand
there are some linux distributions specifically created for sound
or you can always alter your distributon yourself (roll your own)
there are low latency kernel patches and kernel patckes for real time access for user level apps...
and a kernel patch for preemption
most people are using older kernels 2.2.x series patched this way...
i am running this stuff on kernel 2.6.3 on a P4 compiled with intel icc compiler for linux on my super fast linux from scratch and don't have any latency issues even without the low latency patch.
i think these patches might even be included in the 2.6.x series as configuration choices ??????
i run as root when i need to for real time and mem lock access also without the patch.
slackware has audio packages
http://www.audioslack.com/
i would stick with an older faster distribution like slackware rather than a slower fedora or whatever
but i might be wrong about that considering the range of apps from planet ccrma next.
you can transform a fedora distribution using "apt" with music packages put together at stanford
http://ccrma.stanford.edu/planetccrma/software/
the number of programms available here is stunning !!!! many more than i was able to get running on my own
perhaps the best choice
http://www.agnula.org/
i would choose the debian based version
http://www.agnula.org/Members/sama/a_demudi_rc
-- debian is the oldest and most stable/secure and one of the fastest Linux distributions and is a pleasure to use and easy to update/maintain.
try google for Dave Phillips who has done alot of the work and written about the work for some reading
