the 6.4 version makes sense only together with Ubercart!
It allows for defining categories(car, room, boat), unit types(single, double, luxus) and units(room #1, room#2,..).
You can can offer online booking (and payment) of your resources(units) and handle
"walk-in guest" booking(and payment). You can define restrictions together with timeframes,
You can define different rates like (highseason doubleroom, lowseason doubleroom etc.)
...All that now is missing is a detailed docu and an improved userinterface...