I figured I'd try to pick an SEO-rific title to hopefully convey the steps I went through to migrate data from a WM6.1 to WP7.
My Prerequisites: (yours may vary) Outlook and Outlook Connector, OneNote 2007 optional. Thunderbird also works great or so I've been told.
This post assumes everyone has already setup the activesync between their computer and the wm6.x device and the data they want is synchronizing to Outlook. Alternatively I also had the Windows Live app on the phone which allowed for direct synchronization to Hotmail but at the time I didn't want to clutter it up with all my IM email addresses. Skipping Outlook or Thunderbird would be the easiest approach obviously but I found Outlook to be a nice data silo and I could've chose to sync my limited phone number data to the lesser used cloud service.
You have two methods of import, People settings and Email. For the most part the consensus seemed to be to use Settings -> Email & Accounts and People as a last resort. It seemed that some people were having sync issues with Gmail that would only be cleared this way.
You are only going to be able to import Emails, Contact, and Calendar data in comparison to Notes, Tasks, and Docs but you don't really need them.
I basically wrote a bunch of bs to say, hey if you use your client and connect to a web-based email service like Hotmail, Gmail, or Yahoo then you pretty much just push buttons and walk away. My only nag with the process is you can't really say "Don't sync calendar items" until after its set. I rarely care because it does a good job of removing those extra items from view completely but sometimes I don't want to have to remember to do it.
OneNote was a different beast altogether and seemingly a gentle push towards Office 2010 Trial for a smooth upgrade experience. My current method is copying the raw data from OneNote 2007 into the web app version and reapplying formatting. It's slow and cumbersome but at least I can properly categorize what was formerly a mess of notes. I'm still not used to the on screen keyboard yet but that's learned behavior anyway.
(This post was scheduled)