Kubuntu 12.04 "precise" 64-bit
Downloaded, compiled and installed Sigil 0.5.905 without apparent error. (The messages were flying by so fast on my screen, I couldn't read them all. I assume that if anything were *really* wrong it would have bailed out early with an error message.) Launched without hiccups and read a test file. Spell check looks a lot more usable -- thanks. I also am very glad to see the "inspector" incorporated. Just having the computed css available will help a lot.
Here's the only glitch I have found: I try to do a multi-select in preparation for a bulk rename by clicking on the first file name then shift-clicking on the last file name. The range of file names is highlighted in blue briefly, then reverts to only the last file clicked, preventing me from specifing a group of files. End of game, right? Well, not quite. I accidently discovered that if I click and drag a tiny bit on the first file name, then release it on top of where it was before, I can then shift-click on the last file name and this time the entire range stays selected. So, there's a work-around but it shouldn't be necessary.