Turned on Roaming Proflies - Returning from Hibernate is slow

I have some users where I just turned on their roaming profile settings.
Naturally I expected startup and shutdown to take a little longer, and it
does. But what I now see is that most of the time the user's laptop now
takes several minutes to recovery from Hibernate rather than just a few
moments.

The hibernate file loads in about the same time and the user comes up to the
computer locked by xxx screen where they must put in their password. Then
it just sits there for a few minutes.

The user has a pretty clean profile. It only takes up 20 MB on the server
but for some reason returning from Hibernate and even starting up takes
several minutes now despite bing on a GB LAN.

What could be causing the slow speed?