On the planet Wikimedia and in other places, I read posts frequently from disgruntled wikipedians. As I read over these posts, I find myself saying on a point-by-point basis that "Wikibooks doesnt have this problem", or "Wikibooks doesnt have that problem". And while I can't speak for all the sister projects, I can tell you that in my experience, the level of discontent is higher among the Wikipedians then it is among any other community group under the WMF.
I know that Wikipedia does have to face a number of problems that the other sister projects don't face, or that they haven't faced yet. There is the sentiment that Wikipedia is in some kind of competition with other encyclopedias (notably Britannica, which is mentioned most frequently), and also the fact that Wikipedia has grown a fair level of name recognition. When you know that the neighbors are watching, you do tend to put on a bit of a show, after all. Also, because wikipedia has grown so famous, there is certainly the urge for people to write up an article about everything, which has spawned a large network of "notability guidelines", many of which are very strict and rigid.
What the sister projects don't seem to have, or at least they don't seem to have it as much, is the drama. We don't have "factions", and we rarely have "trolling". There is no such thing as a "deletionist" or an "inclusionist". We have never voted to delete our Counter-Vandalism Unit. Bureaucracy, too, is something that many of the sister projects are proud to avoid. To put things into perspective about how little bureaucracy Wikibooks has, I had previously proposed a version of the "KISS" guideline, and the community rejected it as being "instruction creep". In this case, I suppose, the community preferred to lead by example.
Discussions are typically not heated, and very focused on the positive. People are congratulated on their successes, forgiven for their mistakes, and encouraged to continue their work. We block vandals quickly, we don't block our editors at all, and we respect everybody's best efforts.
The sister projects are hardly utopian, and I don't want to make it sound like we are so great, and Wikipedia is so bad. However for anybody who has grown a little weary of the hustle and bustle of Wikipedia, the sister projects share the same ideals of free content while fostering a very different working atmosphere. Sometimes a change of pace is all you really need to get your creative juices flowing again.