According to sources like Tokyohive, they won't have a theater (unlike the AKB sister groups) and already have a senbatsu of 16 of the 36 chosen members.
As shown by various websites they have a young average age, which I think is a good thing. The public in general prefers its idols young, and the fact that AKB48's average age in most senbatsu lineups is about 18-19 (with Jurina kind of throwing everything off) is a bit of an anomaly for idol groups. Another interesting thing is that they won't have a theater, which means that they'll be focusing on other things than getting that together. This is what I think might turn off some of the more serious AKB fans; I know that NMB48 was cemented as one of my favorite idol groups when I saw their stage show and enjoyed it thoroughly. However, this might be good for the group members as a whole. AKB48 and the ultra popular members of other groups (Matsui Jurina, Matsui Rena, and perhaps Yamamoto Sayaka and Watanabe Miyuki) are busy busy people, doing stage shows, promo events, variety shows, etc. This might make the group a bit less of a difficulty than the main ____48 groups are.
The one thing I'm reminded of is when Tsunku created TNX and the Nice Girl Project to be "rivals" to Hello!Project. In fact, it's almost exactly like that. However, TNX ended up being a bit of a trainwreck. Not saying anything about the members, but the sales were terrible and I don't know how much they ended up using that "Hello!Project rivals" concept. Then again, that was introduced far after H!P's peak, so I'm betting that Nogizaka46 will fare MUCH better than Nice Girl Project did.
Only time can tell what will happen with this group, but I'm kind of excited to see what happens!