Writing music for the joy of it. (with Windows 7 64bit, Intel i7 processor, 12GB memory, LOTS of disk space, Finale 2014, Garritan GPO, JABB3, COMB, Steinway, World Instruments, & Soundiron Olympus Micro Choir. And if I ever figure out how to use Sonar X2...the sky's the limit)
You really dont need a "system with midi" since it can output to the several sofsynths that there exist in Linux. If you hasnt yet, you can try with AGNULA distribution, that is pre-made for midi&audio.
I tried Rosegarden out a year ago, but it has changed a good bit since then apparently. However, when I tried it, it wasn't all it was cracked up to be. I prefered Finale and Sibelius over it.
Colton J. Provias
Film Score Composer, Location Sound Mixer, and Sound Editor
Full-stack Web Developer
I've tried it a little bit, using free instrument plugins available under linux. I think it's a very interesting program, and I like it's notation posibilities. Anyway I haven't used it enough because the lack of VST support under linux (no GPO )
It took many troubles trying to get vst's working under linux, and actually they didn't work. So I'm waiting for easier integration in the future to explore more fully the posibilities of Rosegarden.