I just tried out Giga Bowser. He's basically top tier. He's slower than Bowser and he's a bigger target (this doesn't make him easier to combo though. If anything, he's harder as he can't be grabbed), but his ftilt is MUCH stronger than Bowser's (it can KO at 100%), he has longer range than Marth, he can't be grabbed, he can't be stunned by weak moves at lower percentages (for example, lets say he's charging up a smash attack when he's at 0%. Mario throws a fireball at him. He'll still be charging his smash attack, not interrupted. The same goes for other moves like Captain Falcon's neutral A) and as long as he's not smashed out of the boundaries of Final Destination (it's hard to be smashed out anyway, as he's about 1.5 times as heavy Bowser), he can ALWAYS recover back to the stage wuithout grabbing onto the edge, so edgehogging against him would only work in stages like Dream Land 64.
You can practically use him with a couple of moves:
Ftilt - to approach enemies and to edgegaurd
Up B - used incase the enemies get "inside" him
Neutral A - to get people not within Up B range, but close enough
Utilt - to hit enemies coming from above
Nair, fair and bair - used when you're about to land near an enemy