I should start doing this as well (upgrade from 2.4.5), but I'm little worried about all the stuff about the upgrade thing, because the site of course is online all the time, so I wouldn't want it do go down when some possible problems occur, so I don't know what would be the best time for the upgration. Also the language is a little problem when English isn't my best language, so it's quite hard to follow the instructions in English. There is at least dataobject manager and uploadify modules in there, so I've to start reading which part to start upgrading before the other (if there's upgrades for the modules) and weather there's something with the php version as well (in between which stages the php version should be upgraded to get everything running all the time)
The site running with SS is in the root directory and there's other site with the other system in the subfolder. Does the upgrade affect to that subfolder or does it stay untouched?