I have done Heidelberg and can call myself Heidelberg Man :)
It's a great event, though when I did it, it was one of the hottest days in Germany, 33C+ and I rather took it easy. Due to high temperarture no wetsuits allowed, a real disaster for me, as I need a wetsuite to cover up my poor swimming :) I had an aweful swim, but the water wasn't too bad. I think I didn't even made the cut off time and came just ahead of the breast stroke guys. Well, it's all fun anyway. Then on the bike, chasing the others. After 3km there comes a really really really steep ramp, possible the steepest hill in the area, up Molkenkur(?) then you cycle two laps around and up the mountain with some further longish nasty climbs. The bike part is tough, I got lapped by Taubert, elite triathlete. Then the 10k run can be a killer if you put in too much energy on the bike leg. Running was my strength and I passed loads of people, it's 5k up and 5k down the Philosophenweg, the first 1.5k are steep then okay. The downhill just kills your quads. Was really knackered at the end and exhausted, it was very hot, glad I made it without a collapse.
Foggyone, how did you like the event? I grew up in the area and spent all my teens cycling up and down the mountains around the Pfalz. Maxdorf is a very sports enthusiastic community. There are also many little lakes close by too, still open for swimming.