I have been able to navigate on (and download from) the new site just fine, using Firefox 2.0.
I’'ve noticed that the download pages require Javascript for the actual download links to appear (you have to click on a button first, then relevant links are shown). You need to have Javascript support enabled in Firefox (through the ‘‘Tools’’ menu, ‘‘Options’’ dialog and ‘‘Content’’ tab) to use the download page as it is now. Javascript was (at least partly) enabled by default after I installed Firefox 2.0.