Earlier on in Briere's career he produced in the regular season too, he just had injury problems to accompany it which you can't really blame someone for getting a bad rash of injuries. It wasn't until recently that he just stopped producing altogether, at least in the regular season. As others have said though, you could make the argument that Briere earned his contract just with his playoff performances alone.
The thing about Briere is that he's an extremely one-dimensional player. He is or was good for scoring goals. That's about it. He's a horrible defensive player, he's small, he's not good at face-offs (at least relatively speaking to players his age), and he's not even that good at the shootout or that speedy. He just has a nose for the net, he's not slow, and he has a decent shot. Hell, he's even liable to take bad crosschecking penalties relatively frequently.
Coming from a Flyers fan, I wouldn't suggest any team signing him. If he were still capable of being a high-end secondary scorer at the very least then I'd suggest signing him on the cheap, but like I said he's so one-dimensional that even if he were back in prime form he shouldn't be earning what he is now. The reality though is that he's getting old for a hockey player and he's lost his scoring touch, at least recently, and if he doesn't have a scoring touch he doesn't really have any strong points. There's really no reason to have him on your team as a player if he isn't a good scorer anymore and, as is, I don't think anybody can know for sure if he still has it in him.
Just my two cents.