In reply to neuromancer:
If I did it again I wouldn't necessarily wear B2 boots for this trip. We wore them because we were not sure what to expect, and because we already had them and had matching C2 crampons. I wouldn't carry some just for the glacier section, it's not worth it. If you have some B1 boots and can get a similar walking crampon or spikes to match then I think they would be fine in summer conditions, even in rain, and I would just wear them the whole time.
The gap at the top of the glacier (the randkluft to be exact, rather than a bergschrund) was not as bad as thought. We also weren't sure what to expect and had visions of some sort of death defying chasm. It obviously changes with time, depends on how much snow there was the winter before, how hot the summer has been, but it takes years to massively change so won't be that different to when we went last year. You could reach across, take hold of the via ferrata cable, clip into it and step across. My g/f is more vertically challenged at 5'6 and found it a fraction trickier but still no problem.
As we had our own kit I didn't check out hire places but there are plenty of kit shops in Garmisch and I would be amazed if you can't hire the kit.
I would avoid staying at the top. They probably wouldn't let you stay in any of the buildings at the top, and the surrounding terrain is bare and bleak. I love a bit of wild camping or bivvying but IMHO it would be grim and a relationship threatening decision to stay the night instead of heading back down.
We did the route on a Friday, it was busy as we were in the middle of the holidays, and the last cable car was busy. But worth getting down if you can. You can get a train from the bottom of the cable car back to the start of the Hollental route or straight back into Garmisch town centre.
The Hollental hut was being rebuilt when we went which made the decision for us, but if it is open again and if you have time then staying there the night before would shave a few hours off your time, you could stay in the hut or maybe camp nearby, and have a much shorter 'summit day' with a lot more time to get the cable car back down from the top. That was what we originally intended to do but as I say it was being rebuilt which forced our hand.
I have to say we went for a long weekend, Thursday to Sunday, spent the last day looking around Munich, and had an epic mountain weekend. I know the crumbly, bearded, pipe smoking purists (no offence to you all) may say it's not 'proper' mountaineering but who cares - it's a great, fun trip. The route is fun, the views are amazing, they sell beer and chips at the top. Garmisch is very friendly with great food and nice people. What more do you want.
We raved about how great the trip was so much that some friends went out 2 weeks later and did the same trip.
Happy to answer as many questions as you can think of on this. I think it's a real gem.