More and more, I am starting to really like what I see in Denali.
The other day, this headline caught my eye: "ONLINE NON-NULL WITH VALUES COLUMN ADD IN SQL SERVER 11".
In short, it will be possible to quickly add a new non-nullable column to a table. This operation is quick because it is a metadata change. Prior to this new feature, it would be necessary to wait until the server physically manipulates every row in the table. This manipulation would involve exclusive table locking. It would possibly include splitting pages and lots of disk I/O.
This feature would be an absolute boon in a 24x7 system and it should be handy for avoiding lengthy schema upgrades on any system with large tables.
You can read about this feature in detail here.