Well, I forgot to come back and post, but I'm happy to report that everything was perfect.

I paid $16 to hotels.com, and there was some sort of city tax of 2.10Euro per night and that was it.

I am convinced (as I am with priceline bookings, though I've never looked to see if it's discussed) that they give you the crappier rooms in the house, but I've never been sure if that's because they're holding back the better rooms for higher paying guests, or if they don't want to feel like they're giving away the store.

In any case, it was fine and definitely worth the $20...

Now I have another question. The T&C states a "1 free night per booking" policy. This is actually clever because it gives you an incentive to stay at a higher price hotel than you might otherwise look at. But I'm wondering if you can get around this by doing back to back bookings to get two (or more) free nights at the same property?

I might try it this week and will report back if I do.

(BTW, as an aside, I found in reading the T&C that it seems that hotels.com is actually owned by Expedia, since it's Expedia employees and their special prices that are excluded from the rewards program... thought some might find that interesting.)