Things to know before the upgrade to Android 2.3 (Gingerbread)?

Question

I am pretty sure my kit qualifies for the upgrade, and I am quite excited about this. I hope I have made the right choice. Let me tell you, a few days after SE announced that X10 is going to get the upgrade (to Gingerbread) , I couldn't resist the temptation to grab this model immediately, particularly since I was wanting to experience Android OS after a few years using Symbian (my previous phone was N95 - 8GB and Nokia 6600). The price is quite decent for a handset with quite impressive features (8MP camera, etc). My experience with my new phone is pretty good thus far, except for a few issues that we are aware of (eg Flash not supported).
Now, what are the things that I have to know before the upgrade, since downgrading is not supported? I am not a phone geek, and all I have done so far was to back up all my apps (using Astro). I know all the contents of my SD Card won't be affected. I wish to keep all my contacts, messages if that is possible.
Any advice is greatly appreciated. Thanks!
Edit01:
Thanks to Dnny and uliwooly! Very informative replies from both of you. Keep the replies coming! I actually created this thread/post to keep all X10 users updated, and help them decide whether they should upgrade to 2.3 or not. If they choose to, hope this serves as a guideline to prepare them for it.

Answer 1

the Backup and Restore app will work just fine, if its not included w/ the update as SE said,  you can always re-install it
Use this link instead to download the apk
http://www.megaupload.com/?d=I5CJUPJV
How to install it
You need to
go to settings -> applications -> check unknown sources
download IO File Manager
https://market.android.com/details?id=org.openintents.filemanager&feature=search_result
download the backup & restore app, transfer it to your SD card, use OI file manager to find it -> tap on it -> install it
just to play it safe sync your contacts w/ google if you haven't already
open your phonebook
press MENU button -> tap on Send Contacts -> select all -> send it to your email
on your computer
-> download the file -> go to your gmail -> click on contacts -> click on more actions -> on the drop down menu click on "import" -> choose the file -> and click import
"I'd rather be hated for who I am, than loved for who I am not." Kurt Cobain (1967-1994)