I haven't done allocated on arrival before, but I've been to quite a few Greek self catering CHEAP holidays.. All I can say is that you KNOW what the accommodation will be like. Basic. if you're not bothered about that then the only thing to worry about is - will you be miles away from anything, or right in the thick of it? (both no good imo)
I don't think I'd risk it myself. How much cheaper IS it?