John
Interesting observation that Sigil users tend to be Power users.
(
I always thought you had to be a Power User to get Word to do it
your way 
)
I use Book View mainly for proofing, Splitting (when a REGEX insertion won't do), line joining and word spacing
repairs.
CV for just about all else (and undoing some of the artifacts of adding a line before a H tag)
2 things I would like to see
1) a User Macro package for repetitive keystrokes (Eg wrap selected text in a <span... ) BTW if you could figure out how to "Paste into Code" while in BV, this would probably grab a bunch more users.
2) (Wanted,probably due to lousy short term memory) Move the CSS (always in CV format anyway) over to new tab(s) in the Book browser window. It can be used a Coding Reference while editing.