I've gotta say out of all the characters I've used so far, ROB's my favorite. =D Here's a summary of my experience with him, just to add to what everyone else has put up.
His b-up's uber useful, since you can use part of it, stop, and use it again. The only trouble with it is that even when you get back to the ledge, you haven't recharged it yet. You have to be completely on the ground before you can use it fully again.
His aerials are interesting, gotta say that. The fair is pretty standard, comes out fast, and has medium knockback. The uair is a damage dealer, and is his best bet for juggling as it doesn't give too much knock-up. The dair is a good spike, but generally not worth it because of the wind-up time and deceptively low range. The bair is hard to use right, but it's very rewarding if you connect. To get the best hit with it you actually have to be right in front of the opponent, because you move forward a decent amount while using it. The neutral air is very good if you have the wind-up time available. It has excellent knockback, and hits in a circle from below him to above him. Just remember that the wind-up takes a bit, like most of his aerials do.
His smashes are fun. The up-smash, while not hitting very far to the side of him, comes out very quick, and has great knock-up. It's got pretty decent vertical range, as well, so you've got a bit of security if someone's coming down on you. The downsmash will get everyone away from you, either by sucking them in and tossing them up, or just knocking them away if they get tipped by the outside. Very good move for someone who likes to roll around. The f-smash is ok, not one of his better moves, but it still gets the job done.
R.O.B.'s projectiles are awesome. He's got two of them, the LASER, and the gyrodisk. The laser takes time to charge, which is done by not using it, which is simple enough. When fully charged, it's got a decent amount of knockback for such an attack, and is goes through people. You can angle it up or down, and bounce it off the stage, so you should have a relatively easy time of hitting someone with it. It also makes a limited short range attack, as you can sweet-spot anyone that's right in front of you with it, resulting in some nice knockback. His other projectile is the down-b, the gyrodisk. It takes a couple seconds to fully charge, but it's worth it. It has awesome knockback, awesome damage, and you can pick it up again to throw as a regular item. If someone else goes up to it to pick it up, they'll get hit. They can still knock it around with attacks though. Use it to the max, but remember that it'll disappear after a couple throws, so you'll have to make another one.
His throws are alright, no chainthrowing or super KO throws, but they get the job done easy enough. the downthrow can sometimes be used to combo on the less floaty characters, and the side throws are good for getting people off the ledge for edge-guarding purposes.
I don't have too much experience with the tilts, as I only use the d-tilt, really. It's an ok edge-guard, and you can use it pretty fast, so I'd reccomend adding it to your arsenal.
His final smash is fun to use, lasers come out of his eyes and you can chase people and catch them with it, either snaring them in and doing lots of damage or knocking them way back, but both for the most part. It's fun to chase people around with, cause it's a crazy looking robot gone crazier. =D
my one reccomendation for chimp that hasn't been stated is to perhaps be a bit more patient with the gyrodisk, you had a bunch of misses cause you threw it first chance you got, from what I saw.
