I thought it might be worthwhile to post the steps I use to wipe and restore data with new ROM installs again in this thread. I'm assuming you already know how to install the ROM itself (and if you don't, there's an installation guide link in the OP, which I'm reproducing here for your convenience:
http://android.markjohnston.us/DL/LFY/RNOTES/installation.txt).
First of all, I ALWAYS wipe and start clean when downloading a new ROM. I even wiped when I installed the release version of 1.8, from the 1.8c test version. It takes a little extra time and effort, but it's so worth it in the problems you avoid.
Here's how I do it:
1. Purchase the license for Titanium Backup (TiBu) if you don't already have it -- it's worth it -- and go to Batch and use "Backup all user apps + system data."
2. Do a nandroid backup of your current setup, then, using ClockworkMod Recovery, do a factory reset (wipe data and cache), then go into the partitions menu and do a wipe of boot, then of system (even though 1.8 will wipe system and boot for you, I do it myself anyway).
3. Install the ROM zip file.
4. Touch the top left, then the top right, then the bottom right, then the bottom left (in a square pattern) of the screen to skip Google sign in.
5. Make sure you have "Unknown sources" checked in System>Applications.
6. Open TiBu and go into Preferences and make sure you have "Force to same location" checked (this will then make sure your apps and data are restored to the device and SD card, as applicable, exactly as they were when you did your backup).
7. Go into Batch and and start with "Restore missing apps + all system data" -- but
here's the important thing: press "Deselect all" and ONLY check the items in
GREEN (this will restore all your call log, SMS/MMS, accounts, wifi and bluetooth connections, etc.). If you restore the stuff in red, you're restoring system data from prior ROMs, which could cause you all kinds of issues. We'll do apps and data in the next step. NOW, if you're going from 1.71 to 1.8, here's another very important caveat: do NOT restore [SETTINGS/BLUETOOTH] Settings Storage 2.2.1 from "Restore missing apps + all system data" because this will cause FCs in the SpareParts settings in Liquid Tweaks (it's really weird, because restoring that item restored all the Liquid Tweaks data from 1.71, including my color choices in Interface and the data that caused the FCs in SpareParts). Don't worry, Google will restore your bluetooth settings when you sign in. Also, I found out the hard way that the same advice I give here, for going from 1.71 to 1.8, also applies when going from 1.71 or 1.8 to 1.9. I also recently discovered that restoring [SETTINGS/BLUETOOTH] Settings Storage 2.2.1, even coming from another ROM, can cause other issues (for example, if you had a password (PIN) to unlock your phone when you did your TiBu backup and you restore this setting on your new ROM, you may find yourself completely locked out after you set your password on your new ROM and you reboot -- which means that you'd have to wipe and start over again). One additional thing: you won't see some of your data (call log, SMS/MMS, etc.) until after a reboot -- I generally wait until Step 10 when I need to reboot to make my backup anyway, but it's certainly fine for you to go ahead and reboot now if you want to ensure that all your data is there.
8. After you've finished restoring the items in green (other than the one in my caveat above if you're going from 1.71 to 1.8), run "Restore missing apps with data" (these will all be missing items that are in white text) and go through the list and make sure you've got only the items you really want to restore checked. DON'T restore Liquid Tweaks or Spare Parts if they're on your list.
9. Go to Settings>Accounts & sync, Add account and sign in to Google. Make sure Auto-sync is checked and that Sync Contacts, Sync Gmail and Sync Calendar, etc. are checked, and allow them to sync. It's possible that the Accounts restore in Step 7 already restored your account, but you should still look to be sure all your items are checked.
10. Make a nandroid backup of this setup BEFORE you start adding themes and kernels -- that way, it's easy to revert back to stock and start over if a theme or kernel messes you up.
If you run across any apps that restore from Market without your data, because you missed them in your TiBu restore, just go into TiBu and go to filters, type the name of the app, and restore data only.
The only thing left is that you'll likely have to set up your widgets again (at least I do in Sweeter Home 2) and you may have to restore some of your ringtones in contacts, Gmail, calendar and Gtalk.
One other note: if you have Swype, I've found that TiBu restore doesn't work right. If you have the official beta version that you're reinstalling from the Swype beta website, you'll want to reinstall the Swype installer, then Swype
FIRST, before your full TiBu restore, to avoid the memory issues that plague Swype installs.
This wasn't clear, but that's what backups are for, just flashed back to my good ole 1.71 until a vanilla 1.8 is released...
)