Stopped reading the linked paper when it made a mistake because of treating "worlds" as literal things being "split off." Gotta use quantum mechanics if you're going to talk about quantum mechanics. Maybe they corrected it later, but I didn't even want to wade through to find out.
Although they do not "split off" in the same envisioned early on by DeWitt, there is definitely some unanswered questions here. Alastair Wilson and Simon Saunders has raised this issue. Are all the worlds in the wavefunction from the beginning of time or do they somehow spring out from one world? This is called overlap vs non-overlap (first discussed by David Lewis).
Since you are the expert, by all means answer this for us.
http://www.scottaaronson.com/blog/?p=1103
Eliezer's gung-ho attitude about the realism of the Many Worlds Interpretation always rubbed me the wrong way, especially in the podcast between both him and Scott (around 8:43 in http://bloggingheads.tv/videos/2220). I've seen a similar sentiment expressed before about the MWI sequences. And I say that still believing it to be the most seemingly correct of the available interpretations.
I feel Scott's post does an excellent job grounding it as a possibly correct, and in-principle falsifiable interpretation.