I think it depends on where you're coming from, though. You're coming from the east, so 30 makes more sense. My parents drive down from the north and they always take the 13th street exit. Even though it's a straight shot over for us on 30, the hub prefers to get on 35 for that short stretch and take 13th street when we go to my sister's (who lives off Bloomington in the new developments). I usually make him take 30 and then Elwood (it will always be Elwood to me) past the stadium and Hilton, though. I like to give my regards as we drive by.The only problem with that is right now there's not much of Ames out by I-35 that warrants adding more exits, or at least not until they get around to building the mall out there that they've been "discussing" for the last decade. The way I see it, who's going to use a Lincoln Way exit when you're going to use US 30 to get to the west side of town and 16th St to access the north side of town. As it is, not nearly enough people use the 16th St exit to warrant the building of a Bloomington Rd exit and/or a Lincoln Way exit - whenever I come into Ames it's always via US 30. The issue isn't with I-35 exits, as the core of the town is far too far away from I-35 for it to be meaningful anyway. The problem is poor configuration of arterial streets in Ames. Your only main east-west arterial street is Lincoln Way, and the main north-south arterial combination is Duff/Grand, both of which are for all purposes on the eastern end of civilization. Good luck trying to change that, though, because that's where all of the businesses are at.
I definitely think Bloomington could warrant its own exit in the next few years, especially if they keep expanding as they are.