I'd read a lot about XP x64 being unusable. But after installing it on a desktop in 2011, it actually was surprisingly smooth (on my laptop from 2007, the SD card reader didn't have drivers, which was mildly annoying, and I eventually went back to x86). The only thing that doesn't work well is my early-2000's printer, and I don't have a cable long enough to connect it to my desktop from its current location, anyway. I think the release of Vista (Vista x64 in particular) actually helped XP x64 in terms of usability, since 64-bit driver development became more common and a fair amount of that ended up trickling down to XP x64, too.
We'll have to agree to disagree on XP being terrible, though. No point in arguing about that.
I hadn't thought of One Drive integration. The funny thing it's used at my place of employment (with 99% Windows 7 machines, but Office 2010/2013 depending on the computer), but I haven't used it at home since 2011, when I used SkyDrive for sharing pictures (which it was pretty good at). I suppose how much of a benefit it is depends on the home user's use pattern. For the average home user who never makes a backup, it may well be a significant upgrade. I'd rather just use my own storage, and Office 2013's desire to save to the cloud is mildly annoying, but for someone with no backups locally I can see the benefit.
Although what really annoys me about Office 2013 is the informal language. If I open Word 2010 and try to exit without saving, it asks, "Do you want to save your changes you made to Document1?" Very nice, descriptive, and proper. In Office 2013, it says something like "Want to save your changes to Document1?" What type of English is that? Texting English? I'm okay with the humorous sad face in the Windows 8 BSOD, but the informal language in Office 2013 just strikes me as unprofessional.