I know it's not a pick-up, but it is one of two that CNN hasn't called yet.
We had 36 not up for election
We had 12 incumbents win. (AL, AK*, AZ, ID, IA, KY, KS, MO, NH, OH, PA, UT.)
We won 6 open seats (FL*, GA, LA, NC, OK, SC)
We had 1 challenger defeat an incumbent (SD)
36+12+6+1=55
* - AK and FL haven't been called yet.
Holy crap. I was wrong. Will UPdate. Thanks.