The Gmail Notifier was already available (if you could find it), but
is now officially released.
Search capabilities added to Contacts. Contacts is also greatly improved.
Emails can be automatically forwarded to another account. This
service is free for now, but could be a paid service in the future.
And you can save drafts of the emails you are writing.
What will be next? HTML mail?
The full list of new features here: What’s new on Gmail?