You also have to remember that many users have been clamoring for more
WYSIWYG ability: link creation, anchor creation and the wysiwyg formatting of the html code in general... something that I assume was getting harder and harder (or at least impractical and ineffecient) to achieve via the older Book View mechanism with it's highly limited editing menu. Many seemingly casual things were only achievable at all
by going into Code View... which immediately froze many users cold in their tracks. Footnotes for example. The new editor (CKEditor) opens up new possibilities for those users (as well as for the devs).
All in all... even though I didn't really use Book View very much (and I'll probably use CKEditor just as little), I think the changes will allow the more casual users to do a lot of the things they've been wanting/needing to do (without needing to learn how to code); while at the same time, avoiding completely hamstringing the users that already know their way around XHTML/CSS. You know... a compromise
Sure there's some kinks to be worked out, but that's always the case. Hell, I skipped the entire 0.4.x incarnation of Sigil myself. There's just no reason to assume the sky is falling entirely... or forever. Stick with what works for you... upgrade when it suits you... move on if you feel you have to.