It appears that Microsoft have put a fix in overnight because now, according to the status checker, it's all back up and running again.
Photo: xbx.lv/XBLstus
Feel free to let me know in the comments if you're still having issues. Mine seems back to normal this morning although I am hearing whispers that various aspects of Live are still experiencing some problems.
It'll be interesting to see is Microsoft/Xbox put out some form of statement regarding the problems. It was down for a fair amount of time and a lot of people were complaining about losing a paid-for service so they'll want answers.
Stay tuned.