Happy (an oxymoron in this case?),
While I, somewhat, sympathize with your plight you are not helping yourself and your cause by coming across like a person in need of anger management.
First, most of Apple's major OS X upgrades do take between and hour and two hours. Apple Stores may have a better connection to its own servers, but they are still subjected to to traffic over their own connections lines.
So, Apple may have told you an hour for the download, realistically, it is, usually for other users with a decent bandwidth speed, closer to two hours or even a little longer.
Before you left Apple, since it was a long way for you to go, why didn't you check that your Mac was up and running and running well before leaving Apple? Were you that much in a hurry??? Really????
If it wasn't running well, you could've had Apple do a free diagnostics and maybe could have paid Apple to straighten out its issues while you were there?? Hmmm???
Another thing, before you went to Apple, if you were keeping an eye on your posting here, Drew Reese mentioned that the download time drops as the download progresses.
You were soooo fixated on this excessive download time that you didn't even want try to download this update, on your own, one more time, before traveling to an Apple Store, so you could see if the download timer drops as the download progresses?
Also, FYI, having a location with great Internet access doesn't always mean speedy Internet. If a large population of your city uses the same Internet Service Provider (ISP for short) if a lot of users are tapping into that high speed bandwidth stream, the more users using the Internet at a period of time slows down the data transmissions speeds as more and more users tap this data stream.
While I don't defend the Apple's store behaviour over the phone with you, If you weren't acting calm and coming across angry, all Apple employees are trained to not deal with these types of customers, unfortunately. When talking with any Apple location over the phone or in public, you need to be cool and calm and not instigating.
Plus, if you don't have AppleCare, they aren't obliged to offer help over the phone. So, this maybe why you weren't getting anywhere with the phone calls.
As far as all your missing mail, if you didn't set your mail to be deleted off of the mail servers, of the Mail service you use, when you initially download the mail to your Mac, your mail is still on the Mail servers and you can retrieve these if they are fairly recent and you haven't deleted any of this mail directly from the actual mail service account online.
Another thing, sometimes the Mavericks upgrade creates another user account to install the new upgrade.
Your emails may still be there, you need to check if your Mac has an extra created account and if it does, logout of that account and re login to your original user account.
If you find that your Mac is now running slower on Mavericks, please start a brand new thread and describe the issues and It would help us to help you if we could have some more technical info about your Mac.
If you wish, Please download, install and run Etrecheck.
Etrecheck was developed as a simple Mac diagnostic reporting tool by a regular Apple Support forum user and technical support contributor named Etresoft.
Etrecheck is a small, unobstrusive app that compiles a static snapshot of your entire Mac hardware system and installed software.
This is a free app that has been honestly created to provided help in diagnosing issues with Macs running the new OS X 10.9 Mavericks.
It is not malware and can be safely downloaded and installed onto your Mac.
http://www.etresoft.com/etrecheck
Copy/paste and post its report into a new post so that we have a complete profile of your Mac's hardware and installed software so we can all help with your Mac performance issues.