Platform cancel has uses. Almost all of them come on Smashville, with one or two stray uses on Lylat Cruise. Here are a few that I've personally used.
Smashville #1: Fakeout Get up
If you do a jumping get up (press X / Y / Up on the ledge) right as the Smashville platform is floating by, and you platform cancel and immediately fall through, you should get back on the ledge. I've done this successfully in friendlies against a guy that love reading get ups. Fakes him the **** out.
Smashville #2: Anti-Inhale
It's a fact that Dedede is a ****. He'll inhale you just to get you up into the air, where he'll smack your **** with a bair or utilt. The most foolproof way to get around this is to force an exhale when the Smashville platform is somewhere about where you'll be blown into the air. You can regular PC or C4 PC to escape trouble. I've used it in tournament, and people get impressed.
Lylat Cruise #1: Iunno
Shorthopping while stationary will not take you as high as shorthopping while running forward. Lylat Cruise's platforms are at such a height that you can platform cancel and end up on any platform if you do a running shorthop. Normally you would have to double jump to get up there.
That's what I've done with the move so far. Do not ignore anything discovered for Snake! That's why people complain that we're 'so far behind'
This is the platform cancel technique I'm referring to:
http://www.smashboards.com/showthread.php?t=290215