I filed my UAI on the 29th of October and just got the e-mail telling me the investigation was finished on the 17th of November. That makes it 19 calendar days, which according to some stories here on the support forums, is record breaking time. So I guess xbox support deserve a fair bit of credit with that. Did I mention that I also got EVERYTHING refunded? Yeah. That was great.
The point of my post is to give some advice to people who may be hacked in the future, or those that are still waiting patiently for their UAI to finish. I'll try to make this as concise as possible.
If you've been hacked, call support ASAP. Do NOT put your phone down unless xbox support have EVERY little detail from you. Things you will need to give them include: your personal details, an alternate email address for them to contact you and your console ID and Serial Number. I cannot stress this enough. Failing to give them all of your info will only delay your UAI.
To those who are sitting in fear of being hacked after reading all these horror stories, follow these steps as a form of damage limitation. Remove all forms of payment options, including credit cards and bank transfers (paypal). Do not leave any significant lump sums of MS points just sitting there idle on your account. Spend them all ASAP. This hack can happen to anyone and you don't want to give the hacker anything to spend. No website or company can be trusted with your bank details or payment methods. Stick to pre-paid for EVERYTHING. It is so much safer.
Finally, make an e-mail address that is EXCLUSIVE to your xbox live gamertag and NOTHING ELSE. This is vital. Don't let the hacker in on your personal e-mail. Also, go to EA.com and associate your master EA profile with a Live ID that is not used for anything else. If EA are the security hole, hackers will only be getting into a worthless, empty e-mail address.
Sadly, if your account has been migrated to another country, you are in a completely different dirt pile. The problems that arise from this situation are not worth it, so I would recommend not waiting for xbox support. Just make a new gamertag and be done with it until xbox support figure out a way to fix this region migration mess. My account was only financially compromised and fortunately no region migration occured.
That's what I learned from my experience. It can happen to anyone, no matter how internet savvy or secure you may think you are. Until we know where the security loophole is coming from, anyone can be a victim. Thanks for reading and thank you xbox support for sorting this out for me. Good luck with your UAIs everyone!