Yes, installed WPMU when it was 1.0 and haven't upgraded it since. I am aware I will need to move all plugins from respective files into the the functions.php file, but wonder if there are any major obstacles I am missing.
Think the "upgrade" button from the backend will work? There is no info on the website here for upgrading from such an ancient beast.
(rhetorical) also, if I post in the wrong place, can it be re-located?
/face-palm
I'm assuming you'd need to do incremental updates. In other words - go look up the upgrade path for each step along the way. Follow each step incrementally. Not fun. But, I doubt you have much alternative when you're starting from so far back.
http://codex.wordpress.org/Upgrading_WPMU
I would first go to 1.3, make sure that is smooth, then follow the rest on that page (start at the bottom and go up).