Everything worked well - We had no problems!
We booked a Hostel in Frankfurt via Hostelbookers.com and everything worked well. The only small suprpise was, that hostelbookers charged the deposit in british pounds. Afterwards I saw it in the small print, but hostelbookers could display this bigger, because this causes conversation costs. Overall is the site good. Good overview, good rating and reviews system and so on. But it can still be improvement, i. i. e. more transparent or include other rating sites.