I have had our site 188.8.131.52 site fully working, with three test products, with nice modified clean theme, used the Magento Connect to check for updates, and then selected using the drop down list all the modules that where highlighted in yellow, and selected the new updated version (stable) The whole upgrade process went through perfectly with no error messages, I checked.
Upon upgrade, the Magento Connect page cleared and and a message came up saying site is down due to maintenance, then upon f5 browser refresh, I get server 500 error.
i uploaded the downloader and tried a re install, it just kept giving me 404 page not found, or it said it had downloaded the files, but had not, or it just said files allready downloaded. very crappy little file, so i junked that, I then went for a complete re upload of the 1.6 files and went for a new install, that failed, so in the end, i had to do a clean wipe of the server, totalyl empty, then use the hosting\’s auto installer to install a default copy of magneto 184.108.40.206 and then i had to apply all the modifications, theme alterations etc, it was quicker the second time. This has to be the most un helpfull software i have ever used TBH.