I may have missed this (for some reason, viewing this forum causes my browser to act funny, and I don't have the patience to get through all the code snippets to make sure I'm not double posting), but there's a USPS 5.0.0 module in the contribs now. I just installed it, after trying a few fixes (got the domestic options un-metacized, but international still wasn't working for me). Looks like everything is good now for me. Won't work for heavily modified USPS mods, but for the rest of us, it should be good. Remember, of course, to "remove" the module from the shipping modules section of your web-based admin area first.
Mod is here:
http://addons.oscommerce.com/info/487