+1 for the Linux version. I am an architect and have switched all my machines to Linux (Fedora). I have a Windows 7 license running in a virtual machine and the ONLY reason I'm doing that is for SketchUp. I'm running Make right now but if there was a native version offered I would gladly pay for the Pro license.
As for the Linux market share, it may be small right now but it is growing. Netmarketshare shows an increase from 1.63% to 2.33% over the last year. It might not look like much, but Apple had a 4% share back in 2006, when SketchUp for Mac was announced (they're at just under 8% now).