Kelly Blue Book lists a 2007 Prius with those options around $5,500 for "Very Good" condition. The seller clearly has done his homework and knows what he has. I would absolutely look into why the car has a rebuilt title - the seller is not obligated to provide a report but I'm sure you could work $25 off the price if you have one done. He's providing the VIN so he's willing to at least let buyers look into the history.
Otherwise, I doubt you'll have any troubles with the car. My FIL has an '07 with 210k miles and he has not been as diligent with maintenance as he should be. It's still on the original battery pack, too. Even in "fair" condition, his Prius has never had to go in for major service. As not fun as they are to drive, they are very hard to kill.
If the rebuilt title isn't an issue, I'd say go for it. Because of the title, it would also be absolutely fair to ask for a couple hundred off the price.