I'm running the most recent version of Firefox Home (1.0.2) on iOS 4.0. I started loading planet.mozilla.org in Firefox Home and decided that I wanted to open it up in Safari. I went to tap on the action button and found that it was disabled. I had to wait until the page completely loaded before I could click the action button - this took a little bit. This is unnecessary as none of the actions are dependent on a fully loaded page.