I know i'm late on this but I actually still do not have the Pre but I was just fixing up my contacts in gmail in anticipation for it.
Now, the main concern seemed to be that it syncs "All Contacts" instead of "My contracts'
I wasn't in terrible shape as My Contacts had about 135 people, with a bit over 300 in All contacts.
However, here is a quick hint if you have yet to sync Google with the Pre. What I did was after I updated My Contacts, I exported them in CSV format to my desktop.
I then deleted ALL contacts so there was nothing in Google. I then imported the CSV file to My contacts...and bam...only my contacts are in my Google.
So i'm all set for when I pick up the Pre. Note this works better for me as my gmail is really only used for people I know or job related emails....my AOL mail is my junk/bills email box. And my Hotmail/Yahoo is my spam email box.
Hopefully this helps at least one person.