(Feel free to branch this off, if you wish)
1 and 3) In this day and age, I don't think there are many people using machines that can't handle some modest javascript. As for blocking javascript, I'm on the conservative side of that myself: I use the NoScript addon to block javascript. But of course, I add exceptions for all of my trusted sites, and Marcomage would certainly be among them.
If you look at the most popular, most-used websites around, there's javascript everywhere. Gmail, YouTube.. it's ubiquitous.
2) Have you ever tried using Firebug? It's a brilliant javascript debugger. Makes developing with javascript a total breeze.
Anyways, my comment was just some gentle ribbing, I don't pretend to know more than Mojko about web development. The impression that I've got though, is that developing sites in pure PHP is kind of old-fashioned (actually, you can give one of my professors this semester credit for instilling me with that prejudice - she thinks PHP is so dated that she's not even bothering to teach it, we're doing all our server-side scripting with CGI python scripts).