You can make Firefox always show the full url by going to about:config and setting browser.urlbar.trimURLs to false.

Agreed, my biggest current complaint is Firefox expanding the URL bar across the full window right when you start typing. The result is that when you go to edit a URL, it shifts left an inch or two just as you start typing, which stops me in my tracks every time while my eyes search for where the cursor went. Hate it, just like the URL bar expanding in size (vertically too) when you click it. Who thinks these things up?

Note: I never, EVER want a GUI shifting around while I use it!