I'll be in the intro bio, too: was just told that they can't admit me until that class is completed (so financial aid, &c., will have to wait until August). And I spoke with the admissions coordinator yesterday, and she said that the average incoming class is 35-40 strong, so we will definitely not be alone.
I chose Northwestern because of the night classes (I'm going to be working full time -- and then some -- while I do this) and because NWU has a solid reputation.
How about you? Did you look at other programs?