Generic Groupwise to Exchange Migration Advice

Good afternoon folks, I am after some general advice/guideance on a migration project that I am about to start working on.

We're taking a Novell eDirector/Groupwise environment to Microsoft AD/Exchange...I know there's tools/utils that will do the migration but I am just after some general real world experiences/gotcha's etc.

The AD will be a nice new Win2008 R2 AD so first question is, what order should I approach this in..

1. Build new AD
2. Install Exchange
3. Migrate User Accounts/Data
4. Migrate Groupwise to Exchange

or

1. Build new AD
2. Install Exchange
3. Migrate Groupwise to Exchange
4. Migrate User Accouts/Data

To me the first looks more logical but I'm looking for advice from the trenches so to speak....

Also, what utils/tools would you recommend for the migration and co-existence?