Hi, Valloric
These are good questions. I can't see how ads could be a problem not only because I am a Linux user and I will not see them. You need and deserve something, and if this is a solution, sure go for it.
As far as I am concerned, I do not use
bidet even if I am French and for the same reason you gave us -no bloat-, I still use the 0.2.4 portable Linux version which very well suits my basic needs.
Say, one year ago, I used Sigil to split, add meta-data and tweak a little the code (these % for images and so on).
Now, with other automatic EPUB making software around being perfected, I use it only for quick code tweaking of xhtml files, mostly for images display. It means inserting things like
height:100%;width:100%; or these kind of things.
But, seriously, it's really a very useful task. I know of no other practical tool which could fulfill this task so conveniently and I probably will need it for a long time.