A bit off topic: Confirmed Scarlett 18i6 works on Linux with Alsa 1.0.25
Based on this Blog: http://sergey.vlasov.me/2012/09/using-focusrite-scarlett-18i6-in-linux.html
I've just did the build of Alsa 1.0.25 modified as in the blog and the interface now works not only as a standard soundcard but also works great on Jack and thus Ardour.
Switching the pres from Mic/Line to Instrument however is not possible under Linux, only Windows, but as the interface is designed to work standalone also it can be programmed as a workaround to set Pre 1 to Instrument and Pre 2 to Mic/Line.
I just thought it is good info to share, there can be a few users who can make good use of its 18 USB 2.0 inputs + Midi and near zero latency monitoring on Linux.
Thanks to Sergey Vlasov for sharing the information on his blog.