K, Im moving a site from 2003 to 2010 over the weekend, heres the plan:

1) Bump up the functionality level to 2003 native
2) Install 2010 with CA, HT and MB roles on a new server
3) Stop the 2003 server from processing any new mail at 4pm next Friday
4) Start move-mailboxing to move all the mailboxes from 2003 to 2010 over the weekend (about 50gb)
4) Swap the IPs, so the 2010 server gets the IP the 2003 server had
5) Set the 2010 box to do the SMTP stuff and test mailflow
6) Uninstall 2003 from the old server once move-mailboxing is finished
7) Get a certificate so OWA and WM phones work properly

Do I have to do anything on the clients Outlook?

My boss said do:

1) Do ADPREP etc
2) Use exmerge to export mailboxes from the 2003 box
3) Go to the machines with mailboxes over 2gb and manually export them
3) Uninstall 2003
4) Install 2010
5) Import the mailboxes manually
6) Swap IPs
7) Set up SMTP etc
Get a certificate so OWA and WM phones work properly

My way is best right? Im thinking as much in terms of effort as I am in downtime since it isnt important over the weekend.

New server.

I followed my plan and it went well except 2010 is slow as hell compared to 2007 - owa takes forever to load, the transport service takes like 5mins to restart, the management console takes ages to do anything in...

Agggh.

Ive got it almost done but I got problems:

1) 4 mailboxes didnt move and exmerge aint working, neither can I open them in outlook anymore so Im recovering them from backup... +4 angry users.
2) Since the new server went in the domain controller has ground to a halt, even though CPU and memory usage are low and Ive tried rebooting it. Every mouse click takes 5-10 seconds to register.
3) Possibly related to 2, things like opening the address book in outlook and bringing up a contacts properties takes forever.
4)

Server is a Xeon with 8gb of RAM with 65 users.
Im thinking maybe make the old mail server a second DC and GC server.

hehe that tick box caused 5mins of panic on day 1.

Sorted most of the probs now.. the slowness was down to the DC and delays in queries to the GC from Outlook - adding another GC and pointing the clients at it fixed it.

Now Im wondering if I should uninstall Ex2003 proper or just turn the old server off...

 :| Got a stupid problem now where a couple of users get incorrect password when they try to log in to OWA even though theyre using the right creds and it works for everyone else..

Got it working now, bloody AV issue of all things

Anyway, the DAG stuff is really impressive, but you need 2008 enterprise server or it says no