We're exploring options for stops on a drive between Kassel and Meersburg. One idea is an overnight in Baiersbronn for a hike and Michelin dinner or drive straight through to Bodensee with lunch somewhere interesting along the way. Would appreciate your advice.

It is about a 5:30 drive if you take the E43, and that would take you right by Rothenburg, Dinkelsbuehl, Nordlingen, Feuchtwangen, etc. at about the 3 hours mark. Any of those would be a good stop for lunch and a stroll.

As aramis said.
Just a caveat.. Road signs in Germany do not always show the E number (europe route). The motorway that you would take south if you don't stop in Baiersbronn would always be signposted as A7, or just a white 7 on blue.
If you are a real foodie, the detour via Baiersbronn will sure be worth it. The surrounding scenery of the Black Forest is "nice" but not necessarily breathtaking.
You should make the decision based on how much you want to eat in Baiersbronn.

Thanks for the great advice! Still undecided about Baiersbronn since it is a bit off the direct route and there are other Michelin restaurants during our planned stops. Appreciate the input.

Well Ulm a good visit down by the river some very pretty buildings.

Further south http://de.wikipedia.org/wiki/Schloss_Mochental is a very odd castle and there is a bar/inn next door

Haven't been to Ulm and like university towns so putting this on the route. Thanks for the suggestion. The architect might be interested in seeing the castle, too! Thinking now we might forego Baiersbronn this trip and overnight in Rothenberg and visit their notable restaurant. Thanks, all!