i used to hate rebuys because of how crazy they were pre-rebuy break
But now my view on them is this: basically they are freezouts, but with the added feature of being able to rebuy before the first break.
People will pay you off 90% of the time pre-break because they play like maniacs. The prize pool gets much larger, and basically it's easier to make big money in these tourneys.
What generally happens is, the gamblers build huge stacks by the rebuy break, and if you're a smart tight-aggressive player, you should have a decent stack by the break aswell.
This is good for me, because usually by the time the break comes along, i've set a supertight image, and can now steal the 100$ BBs pretty easily.
On top of that, the big stacks provide an easy double-up because most of them are donkeys or gamblers.
Another thing is that the prize pools can be much larger in rebuys. I recently played a titan 6K, but there were so many people making so many rebuys and addons that the pool reached over 8000$
another thing to consider: when you look at a rebuy's buy-in, consider that you'll most likely pay 2-4 times that in rebuys and addons, so a $5 rebuy is really like a $20 tournament.