Differences in car rental companies - need the dirt on pros & cons!!

[Anal Annie]

OK, so I put in a rate watch for a rental car for a week on Oahu earlier today through this rentalcodes.com site that I saw mentioned here. I selected about 6 different rental companies although I've not used all of them before. I've used National, Alamo & Enterprise for sure. Anyway, I just got an email with a lower rate with Thrifty that beats my requested bottom line (I put $295 because most were running $340+ for "full size"). Anything wrong with Thrifty for car rentals? How do most of them differ? If I got this offer on my first day do you think I could do even better? I figured rentals in Hawaii would be high - but should I shoot for even less? This deal was $271something with the taxes. Does anybody have any experience with rentals from the Honolulu airport? Pros / Cons? Locations? Should I just grab it? Do most of these car rental companies have the same cancellation policies? I wasn't expecting a response on the first day! Now what do I do? It says it expires today...