OOo, the program, sucks. Office2007 is somewhat of a heavy pig, but even that is faster and more comfortable to work with than OOo. And while I was really skeptic of the ribbon interface, I'll grudgingly have to admit that it's something that's grown on me - it actually does make editing faster & easier. (All versions of office suck wrt. multi-file documents and externally linked images, though).
As for ODF, that sucks as well. A bit less than MS's OOXML, but it still sucks. Just as OOXML, it's basically a messy memory dump, it's not super compatible between versions, and it's not properly documented - one of the developers working on gnumeric has a bunch of nice details about this. Also, it's outright insane using zip+xml based documents for anything but document exchange... which you'll realize as soon as you're working on anything larger than a "dear mum" letter.