I happen to think Ike's usage will increase a good deal as the game advances. First the bad news, Ike has a handful of counter matches, and while low in number, they're really hard, and he'll probably be used seriously only for counterpicks. Namely DDD, Pit, and to a lesser extent, Metaknight.
Now onto why I think Ike is a good character. First you have to look at Brawl mechanics, as they largely favor Ike-
Brawl is slow, so range is more important. Where speed vs range is normally debatable, range dominates hard in Brawl. While other characters will trade hits for 9% a hit, Ike will attack other attacks, beat them, and do double back anyway.
Brawl has no combos. Again, another debatable point is combo potential vs kill potential. With much more pronounced DI, very low hitstun, and higher % kills in general, being able to kill against good DI is suddenly much more important that combo potential. You have to assume that your opponent will be a good player at all times or else the character isn't good, only good vs people that suck. Where good players will survive attacks from weaker characters, they won't survive Ike's. Where good players will DI and dodge out of Ike's combos....well, they won't. But they will DI and dodge out of combos from other characters too. I feel that high level play will consist of very few combos and higher % KOs as people learn to DI better. Both of these trends will benefit Ike.
Brawl has more pronounced DI, and therefore more effective DI. As DI improves, it will be harder and harder to gimp Ike players, as they typically play on Ike's weaknesses in his recovery. Ike players will overcome them, he has the tools to do it. Not only that, I think Ike players will learn to gimp opponents back. Aether is an AMAZING gimp killer, especially from the edge using the spike. However, I think Ike will get better at gimping other characters back, since he can usually go out further than the opponent expects or can deal with it, and just hit them with something strong to ensure a KO.
Brawl offers fewer technical aspects. Technical play offers options. With fewer options, free attacks and ways of negating mindgames becomes more powerful. Ike has tons of ways to guarantee a hit that most characters would be jealous of.
-ike's upair covers the ENTIRE platform for all 3 platforms on battlefield. Also, you can reach the 2 side platforms with upair. SH upair will guarantee a hit with even mediocre timing rather than needing a guess to hit them. You can also mimic this with his fair.
-ike can kill a ledged opponent, easily for that matter. Actually, for the standard character, there is -no safe way- to get up from the edge against ike's SH fair. Sure, Wolf can over B through the stage. I can't think of anyone else with a means to get past ike's fair to get up on the stage.
I'll add more tomorrow when I have time.