The Connect Agent is required to do an on-line, or 'hot', backup.
I just did a restore from the Connect Agent when we upgraded our server.
The old server was running on some Pentium Pro 200's and it was getting a
little overwhelmed.  So, we built a new server with dual PII 400's and
500+MB of RAM.  We loaded Exchange from the CD and then the Connect Agent.
I then restored the Exchange Databases from the Connect Agent, and
everything was there and was exactly the same.  the onl;y difference that
was noted, was that our IMC was not configured correctly anymore.  but, over
all, a minor problem.

Hope this helps!

Nathan J. Norrgard
PC Systems Administrator
Liberty Bank
860.638.2938
NNorrgard AT Liberty-Bank DOT com