I never really thought about him, and now that I've seen him I'm disappointed. First of all, his Pikmin can be attacked, which is a very big deal, and I'm pretty sure you aren't going to just be able to pluck more Pikmin out. Why? Because a skilled opponent will be keeping the pressure on and using attacks that have hitboxes out for a while (neutral air anyone?) to hit Olimar and his Pikmin. In Melee, you never see a good Peach player pull out turnips when the other player is close, because the Peach player knows he/she will get attacked or grabbed or whatever. I think it'll be the same with Olimar, unless Brawl is a lot slower than Melee's advanced metagame.
Another thing about Olimar I don't like is that his other B-moves look really bad. First there's the Pikmin throw: I really don't think this will be very good. It doesn't sound like it has much range (like maybe half of the distance of FD or less), unless you're throwing a yellow one, but the chances of having one of those in the lead at the time is unlikely, and there isn't much you can do about it once you've realized that it isn't there. Anyway, if I were far enough away that you could throw one and have no consequence for the lag time, I think I'd have plenty of time just to hit jump and evade it. Any closer and I'd be able to jump regularly, and maybe even short hop and/or hit you afterward. Oh, and if you miss, I'm pretty sure that means those Pikmin won't be as much use to you as they probably won't be able to assist you in your up B recovery since they will be wandering around (now that I've jumped over it I'm close to you again, so calling them would get me a free hit). It really looks like one of those B moves that won't ever get used later on when the metagame evolves, like DK's down and side B, Fox's side B (not for recovery).
Speaking of recovery, I REALLY don't like Olimar's recovery from the way it's looking. First of all, let's just face it: you probably won't have 6 Pikmin at all times (if you need to recover, it probably means you are taking a beating anyway). Secondly, and most importantly, is what I made my own thread for. If your Pikmin can be attacked while in the chain, then Olimar will have some serious problems against edgeguarders. I can camp on the ledge and then drop down, double jump and attack your Pikmin and then use up B to get back to the ledge again. Even if you can't attack the Pikmin while the chain is there, it seems like it'd almost as easy to just go for Olimar who won't be that far away from the stage since you probably don't have six Pikmin.
The whistle move is a waste of space. Olimar is already at a disadvantage by having his Pikmin be able to be "unbound" from him at all.
My last concern is fighting without Pikmin. It looks like if Olimar runs out of Pikmin, he is completely screwed over. As in, he doesn't even have a fighting chance to survive. Just look at his limbs, they're so short and stubby! I'm gonna go ahead an guess that his range will suck without Pikmin. That means that now pretty much every other medium-fast character will be able to keep a barrage of attacks going, and as long as they don't stop for too long, Olimar won't really do anything about it.
There's one more thing I'd like to point out about Olimar.
Everybody looked at this image and thought their problems were gone. However, I look at it like this: sure, Olimar may pluck fast, but look how long it takes them to touch the ground (thus be usable)! If somehow you get away from my relentless strikes and pull out a Pikmin, you still have the same dilemma for about another whole second or two, which is just enough time for me to get you into the air again so I can finish you off, or continue to combo you.