I've had my Eleven Rack for just over a week. I bought it mainly for use as a performance tool, assuming that I'd ignore the bundled Pro Tools software. Any recording I do with the 11R will use my existing recording rig via an analog connection.
I very briefly flirted with the idea of trying to install Digidesign's Core Audio drivers in order to use the 11R as an interface for other audio applications on my Mac. After three frustrating (and ultimately unfruitful) hours of trying, I unravelled all of the mayhem that the Digidesign software installer had visited upon my system. It will be a cold day in hell before I next attempt to run *any* Digidesign software on my computer.
On a more positive note, the 11R seems deliberately designed to appeal to players of "my vintage". The amps and effects, though few in number, cover the classic sounds very nicely. The Tweed Deluxe model alone sold me on the 11R. I also found the tape echo, Leslie and reverbs very appealing.
The 11R has a shallow learning curve and yields impressive results with very little effort. I had a performance-ready patch set up within fifteen minutes of sitting in front of an 11R for the very first time. That's not something I was able to achieve in several hours spent with the big-$$$ modeler with which everyone is so enamored. Sometimes getting a great sound by adjusting a few really simple controls is more useful than being overwhelmed by options.
Like all good modelers, the 11R performs best when paired with excellent amplification. You'll be disappointed with the amp models if you try to run a good modeler into a guitar amp and cab. At home I play through a PA built from QSC K-series powered speakers. When I play out (which I haven't done yet with the 11R, but have been doing with other modelers since January 2007) I simply run the modeler into the stage snake and let the venue's sound guy take care of the rest.
I've collected some other thoughts and observations regarding the 11R here