Lucario's roll is the second coming of Jesus. It's that good.
Lucario is the ****.
Impressive range+lingering hitboxes+high priority, ****ing annoying projectile that can kill you very easily if you're caught unaware, solid aerial game, can actually pull off some inescapable combos along with HUGE strings of attacks that are hard to get out of, jab cancels, solid ground game (Fsmash. FSMAAAASH), decent recovery (No, it's not terribly easy to gimp unless you knock Lucario waaaaaaay out) and the aura boost. He's also very floaty. =DDD He's also a slippery target and can make a pretty good defensive wall with his good aerials and DI.
Lucario is a very balanced, very solid character. His only real weaknesses from what I've seen are difficulty finishing opponent's while he's at a low percent, he's outranged by Ike (But has quicker start-up on most attacks), he puts a lot at risk if he tries to approach Ike (Which he shouldn't be doing) and he has no way to stop opponents from intercepting his recovery.
Ike can kill Lucario &#$%(#$ early. He racks up damage quickly, but that also works against him. Ike has to play carefully as he gets Luc into the killzone. Ike's range helps him do that quite nicely.