All I can say is... What took them so long?!
Based simply on the number of fanboys/girls I've talked with on these forums and others, I'd say that Rozen Maiden will do well in the R1 area. I'm biased of course. Anyone who bashes the series because "its popularity is based on a bunch of 4chan memes" can bite me. While it certainly isn't Bleach or Naruto, for a simple 12/24 episode series I believe it will do well.
The license couldn't have come cheap. I wonder how long Geneon considered this before taking the dive; how much research was done? Bunches. Companies make money. And Geneon will definitely be taking mine come release time.
edit: Yeah, I've got 4 of the R2 Japanese DVDs, which probably cost me about the same as the whole season 1+2 will cost me of the R1 release.
Plus they'll have subtitles...