Mario is really good in Brawl.
His projectile game is better partly because of the physics engine and because he's more nimble. He can approach better with Fireballs, he can stop ledgeguarders better with Fireballs, yeah. Fireballs are seriously GOOD in Brawl.
The Cape, contrary to popular belief has NOT been nerfed. It is just as useful as it was for ledgeguarding because it can push people away from the stage so they don't grab the ledge. It also reverses controller orientation briefly, so if someone charges a Firefox to the left and gets caped, instead of going left, they will fire to the right. The Cape can still do everything it could do in Melee, and due to the lack of powershielding projectiles to reflect them, it is that much more useful.
The FLUDD is amazing for ledgeguarding. It will gimp some recoveries if fully charged and if it gets a clean hit. It's hard to explain, but it makes ledgeguarding a LOT easier, by persay reducing the benefit opponents get from using recovery moves. You should watch Mike Hawk use the FLUDD.
Mario's air game is still fast and great for juggling like in Melee. He has a little more range on some attacks, which helps a lot.
Mario didn't get too much more in terms of kill strength, but his Up-smash is a lot easier to connect, and his F-smash doesn't demand nearly as much sweetspotting in order to kill.
Overall Mario is significantly better. He's a character that is awesome at ledgeguarding in a game where that is difficult to do. He still has a lot of variety to adapt to situations in Brawl. his shortcommings are still range and kill strength, but as far as I'm concerned he suffers from those problems less than he did in Melee.
