Hi Kevin,
I read Eric's post when he posted it, and Molly Holzschlag and I discussed these exact issues with the Blue Flavor guys when they were in the studio. I think you might be confusing a few things. Leaflets are definitely web-standards -- they don't use any proprietary Apple stuff. Everything there is W3C standard.
Eric's issue is more generic. He's talking more about web sites than about RIA-style applications (leaflets definitely doesn't act like a web site, it behaves like an app) It is quite possible to use web standards and yet not be cross-browser. Especially in the mobile space, web standards support has not been complete enough to support the rich kind of functionality you can get in desktop AJAX while being cross-browser. While your Palm probably doesn't have the necessary level of standards support, if you used a browser like Opera Mobile/Mini, leaflets could be made to work.
If you want a rich UI app that runs identically on a wide range of mobile devices today, you don't really have any options. Maybe Java? That's what I think is so remarkable about Leaflets -- it's the first example of an app that is able to compete with a proprietary runtime look/feel, using only W3C standards. It suggests that web standards still may have an important role to play in mobile, as other devices embed browsers with better standards support.