Before I submit my opinion on Jimbei, I must ask: Did anyone but me find Arlong really, really weak? Let's start with his fighting style. Arlong used his teeth to bite Luffy with mostly, which showed me we was a terrible fighter. To bite someone, you have to lunge yourself at the person, leaving you completely open for attack. Even when he DID bite Luffy, it's not like it did much. Second, his nose, everyone talks about how he used his nose a lot in his fighting style so I must also ask, when did he do THIS? I remember him using his nose one time, and that was when Luffy broke it. Again, since you're leagues taller than your opponent, anything on your face is automatically useless, so why even bother using it? Next, him using his teeth on his hands, I found this to also be useless. What exactly did Arlong to with these that hurt Luffy all that much? Absolutely nothing, from what I saw. That also made Luffy using them seem all the more stupid. The only reason I see why Luffy didn't just beat him up was because he took the time to talk to Arlong about how you don't treat people like shit. Anyway, I just had to get that out into the open.
Now, onto Jimbei. Luffy KOing him on the spot is utterly ridiculous, despite them only talking about his power once (which again baffles me why people talk about how he's been "hyped up"). You must remember that he is a Shichibukai and therefor, very, very strong. This obviously won't be some kind of "Oh, hey Jimb- GOMU GOMU NO PISTOL! Yay, he's dead. Let's go get some jerkey" kind of thing, if they do indeed fight. Why would they even bring up a Shichibukai if he can't even take a single rubber punch? This isn't someone incredibly lame, like Bellamy, this is a merman WARLORD OF THE SEA.
As for his bounty, I'm guessing it froze at about 300million, just like Luffy's current one. Although, I don't have a problem if it was lower, it would just be interesting to see Luffy fight someone who was of equal interest to the World Government. This is, of course, if they even fight at all.
Closing thoughts, I hope Jimbei will be REALLY different. Like a huge, menacing merman in the shadows, just to start dancing around in a tutu and singing about sunshine and daisies.