I like the way that the Big 10 made maintaining most of its rivalries a priority. Save for the Iowa-Wisconsin series, they were able to keep the rivalries a part of the overall landscape in college football.
Commissioner Jim Delany stated repeatedly the past several months that the Big Ten would prioritize competitive balance and protecting rivalries in forming its as-of-yet unnamed divisions, and I'd argue the league successfully achieved that. Each side has two of the four "glamour" programs (Ohio State and Penn State in one, Michigan and Nebraska in the other) and one semi-regular title contender (Wisconsin in the former, Iowa in the latter). And nearly every important rivalry will still be played annually, with the notable exception of Wisconsin-Iowa. (The Badgers are the one team with a legitimate gripe about their placement.)
Meanwhile, Nebraska's impact will be felt almost immediately upon its arrival. When the Huskers' 2011 schedule scrolled across the Big Ten Network ticker, the first two games to show up were "at Wisconsin" and "vs. Ohio State." They'll spend their first November playing at Penn State, at Michigan and vs. Iowa. Think those games might get some eyeballs?
As far as new rivalries go, I think that the Iowa-Nebraska series has all the makings of a natural rivalry. By that I mean that it derives up from the fanbases of both schools, not down from some Bill McCartney-esque intelligent designer.
You have neighboring states that have flagship football programs that have been very good at the same time. Of course Nebraska has the overall edge on success, having won five national championships. But I recall when I lived in Omaha back in the late 80's and early 90's that fans from each side were chomping at the bit for their teams to play. The Iowa fans wanted the Hawks to show that they could beat the Bugeaters and Cornhusker fans wanted the Huskers to put the Hawks back in their place.
Time will tell if this is a good rivalry or not. One or both teams could go into the dustbin of college football and the series will become an afterthought. But if I were a bettin' man, I'd bet this becomes a nice rivalry.