During my customer's migration from SPS 2003 to MOSS 2007 testing environment, we encountered some challenges while migrating My Sites. With Bill's help, I was able to fix the My Sites in testing environment. During the actual production upgrade, My Sites were sucessfully migrated.

Here's a recap of the fix I did in the MOSS testing environment:

1.       Migrate the portal content db first. 

stsadm -o addcontentdb -url http://sharepoint07uat.corproot.com/ -databaseserver dbserver -databasename portal_SITE

2.       Create a web named something like “my” using My Site Host template under the portal

stsadm -o createweb -url http://sharepoint07uat.corproot.com/my -sitetemplate SPSMSITEHOST -title "MySite Host"

3.       Then restore SSP from the old PROF db: 

stsadm -o restoressp -title Restored_SSP -url http://adminserver:11111 -ssplogin DOMAIN\sharepoint -mysiteurl http://sharepoint07uat.corproot.com/my -indexserver
indexservername -indexlocation "d:\index” -keepindex -sspdatabaseserver dbserver -sspdatabasename portal_PROF -ssppassword pwd

4.       Execute iisreset 

Then go into the SSP admin, check My Site settings, search settings, User profiles to make sure they all look good. 

5.       Now as a user, when I click on My Site in portal home page, I’m brought to http://sharepoint07uat.corproot.com/personal/userid and when I click on My Profile (or others click on my name) I’m brought to http://sharepoint07uat.corproot.com/my/person.aspx?accountname=DOMAIN\userid

6.       To see the old SPS2003  MySite home page, just type http://sharepoint07uat.corproot.com/MySite . The Web Part error in this page is expected due to the retirement of My Alerts summary web part in MOSS 2007. Other web parts from your old MySite home page should show up here. This link can be pinned at either SSP or site level.

I'm also linking Bill's blog here for further reference:

http://blogs.technet.com/wbaer/archive/2007/02/19/co-hosting-team-and-personal-site-collections-within-an-individual-web-application.aspx