There are two things you need to be aware of at the outset:
- Live @ Edu has limits compared to on-premises hardware (and this affects migrations disproportionately)
- Going from on-premises hardware to Live @ Edu is just as major a migration as going from (say) Oracle Calendar Server to Live @ Edu.
Now let's talk about going from on-premises to Live @ Edu:
First the voice of experience, in this case a user going from E2K7 to Live @ Edu:
Yes, you CAN devise and execute your own migration process. But but do not plan on it being either simple or fast.
Second, we have the voice of authority, Microsoft, warning about this:
So Microsoft is working the IMAP mail migration angle (be sure to test how long it takes), but calendars, contacts, tasks are not included.
Third, we have the voice of Sumatra:
If someone is moving your calendars, ask if the meetings come over live with guest lists and responses intact.
Our general recommendation: If you're looking at migrating from a legacy system and considering going into Live @ Edu sometime down the road -- all indications are that it is better to make your end-point decision FIRST. It will save you tons of work down the road.