Tom!
Thanks so much for the recommendation to try the Neckar valley. We actally drove along the Neckar from Heidelberg to Bad Wimpfen, stopping in Hirschhorn for lunch at DEBO 800 (we're Americans after all :-) and Burg Hornburg for spending money (ditto) - we also walked around to see some of the sights. The GPS went insane once on the way and we ended up on a 2 car ferry across the Neckar to a 'K' road - but we did end up all right back on the river road and the excursion makes for a great story.
Bad Wimpfen was really chosen because it was convenient to Heilbronn - our traveling companions wanted to visit with some German friends there...BUT...
I found the town positively delightful. The views of the Neckar valley (from the bluff the town sits on) in the mornings were wonderful, walking from the hotel through the lovely park each evening to a restaurant was a great way to slow down after a busy day, the Blue Tower and the Red Tower were quite interesting and I loved walking through the old town wondering how all those crooked houses managed to keep from falling over (it actually looked more medieval than walking around Rothenburg IMHO). The afternoon we arrived there was a re-enactment of some sort going on that was also fun - I don't know how often that happens.
It was easy to get to and from the hotel to the A6 - we went to Heidelberg one day (40 minutes to the Kornmarkt parking garage, I love autobahns), and another day we went to Rothenburg (55 minutes to the 'West' parking lot). We didn't take any trains so I can't speak to where the station was.
There were a good selection of restaurants with local specialties within walking distance - including a lovely Ice Cream shop run by some Italians who each night seemed to be heatedly debating some important topic of the day...They always had time to give us a smile and to make us one of their ornate sundaes though.
All in all it was reasonably convenient, inexpensive, friendly, quiet in the evenings and had a good selection of local sights to fill the time we were there.