Just going by what I see as an outsider reading things like this:

http://forums.precentral.net/homebrew-apps/203951-webos-quick-install-contd.html

and this:

http://www.webos-internals.org/wiki/Application:Preware#Installation__Steps

Easy enough for me, but not something the average joe would/could do. But I wholeheartedly agree that there are far fewer average joes using a Pre than an iPhone (or touch for that matter).

I've edited the previous post to remove the "anywhere near" as perhaps it was a bit strong. For the iPhone you'll find utilities that both jailbreak and automatically install the app management/repository application(s). You don't need to know anything about repositories yourself nor change/alter anything once you start the process.

The iPhone process isn't exactly very joe-friendly either, but it has more history, media coverage and word-of-mouth which does push a lot of joes into making the leap. A lot of clearly written tutorials, that for the most part say "download this, run this, press a button and you're done"