"My experience using other booking sites for 'cheap deals' has been that you're often treated as a lower-tier customer, for example being given worse rooms (ground floor, no windows etc). The HotelTonight experience is the opposite. ~25% of the time, I receive a room upgrade without asking"

They're all OTAs. You're just as likely to get a "good" room with HotelTonight as you would with Priceline, Hotwire, etc. The quality of room you receive is mostly dependent on room availability and the check-in agent.