Okay, so I figured out what was limiting my use of the Platform behavior! With Jump Strength, you can't change jump height and jump speed seperately. If I want a guy to jump 450 pixels at 150 pixels/sec, there is no way to do this with the Platform Behavior. This really ruins it for my platform game. It seems (unless I'm wrong) that I have to use Custom Movement, which will be a hassle from what I've already tried with it. I might try a combination of Custom Movement and Platform Behavior, but I suspect some of their features won't coexist correctly for what I'm doing.
For example, since I felt as though the built-in Jump Sustain was inadequate (and yes, I was using it correctly, even in examples I've seen it doesn't look right), I decided I'd make a triple jump system. This would arguably work better for the style of my game anyway, but when I tried making it, the inability to alter the speed at which the jump is made ruined it. I needed three jumps of a certain height, each made very quickly. I have also noticed that I couldn't make a jump in the middle of another jump, though I am not 100% certain (though pretty sure), that it isn't just my fault on the Event Sheet side. Basically, unless I can add complexity to jumping in my game, it won't be a good platformer.
Note: I don't post .caps because I don't want people stealing my game. No one outside of my beta testers will play it until they accept an EULA
Edit: Okay, while playing New Super Mario Bros. I noticed up very close inspection that Mario's Jump Sustain does have the tiny pause or lack of smoothness whatever that the Platform Behavior has. Maybe it is more noticable in Construct or maybe just with my sprite (and since I have no animation yet, even the tiniest things stand out in a jump), but I should be able to make it look good enough. Still, it is essential I find a way to alter jump speed. One reason I need it is to help add more variable height to Jump Sustain. I noticed Jump Sustain is very much tied to Jump Strength. If you tap Jump, it will go as high as the Jump Strength/Gravity allows. This is the minimum jump. Now, if I alter the Jump Strength/Gravity to make the minimum jump smaller but have a sustain that makes it basically jump three times (since that is pretty much what Jump Sustain does), the speed will not feel right.