Somewhat old news, but may not have the visibility of other stuff, particularly as it's Linux-centric.
Jorgen Aase - founder of xtsoftware and creator of the highly innovative energyXT has a native Linux version of energyXT2 available. I'm a long time user of eXT1 on Windows and it is truly a "Swiss army-knife" for audio and midi. I was extremely excited to hear about native Linux support, with no compiling
I've run eXT2 on both "vanilla" ubuntu and openSUSE via JACK, and it runs very well. Other users report eXT2 running well on all sorts of distro's, particularly media distro's such as JAD or ubuntustudio.
I sequence on an ubuntu laptop using eXT2 and slave my WinXP GS3 box. My next phase of "hacking" is to run the real-time kernel as well as WineASIO, but those are another topic.