No offense, but you're missing the point.

The majority of ASP.NET applications that you'll find online have relatively massive viewstates (though, I've noticed that dotnetkicks has a very lean viewstate. way to go, guys). Even if you can compress all of the response HTML to negligible sizes using gzip, the viewstate round-trip alone is usually significant enough to try to avoid when not necessary.

You're also ignoring the performance cost of reinstantiating all of the controls and running them through their life-cycle in order to render the UpdatePanel's HTML.

Compounded across a respectably sized user base, the savings are absolutely worthwhile. Especially given how easy web methods are to implement.

The ViewState is already compressed. You won't achieve anywhere near that kind of result compressing the ViewState. I'd be surprised if you compressed it even an additional 10%, best case.

I'd assume /kick on a URL that isn't in the database yet will automatically go to /submit. So, using /kick is more robust when you may have people hitting the bookmark on pages already in the database without knowing it.

I can't think of a time FireBug has ever let me down. If you haven't tried it in awhile, give it another go with the release version that's out now.