Do you use more than one computer?
If so, you're missing out on some of my favorite features (i.e. automatic roaming of system and app settings, WiFi and web form passwords, etc).
I tried it, but noticed that it simply did not play well with accessing other my Windows computers over SMB. Which I do a lot of. I have Gigabit Ethernet and 5GHz WiFi, I map the C drives of all my computers (e.g., computer #1's C drive is always network-mapped to "J:" on every computer on my network, including computer #1 itself, computer #2's C drive is always mapped as "K:" on every computer, etc., and I also use NTFS mount points, so if I wanted to access the second optical drive of computer #2, I can just punch in K:\Mount\F from any computer on my network) Makes for a nice and consistent way to easily access all the file systems no matter which computer I'm using... and it seems to not work very well if I use Live accounts. I get mysterious (and sometimes intermittent) connection and login problems, all of which disappear when I switch to using local accounts. That's the primary reason I don't use Live accounts.
The second reason is that I'm one of those old-school people who grew up with DOS and Windows 3.1 and like to know exactly what's going on and doesn't trust "automatic". E.g., exactly what does and doesn't get sync'ed (I think it's safe to assume that my rather large Firefox profile in %AppData% doesn't get sync'ed), how do I know when things are in or out of sync, how conflicting settings get resolved (e.g., if I set an option to A in computer 1 and to B in computer 2, what exactly gets synced?). So I personally feel much more comfortable handling things manually and deterministically so I know exactly what is going on and exactly what the state is.
In any case, I do concede my choice to avoid Live accounts is very much tied to my specific (and probably unusual) way I do things--it's just not for me.