Hi,
Basically one of the most valuable things to an end user is their profile. This environment takes years to develop and if wiped months to get it back the way you remember. Think of all the spell checker customisations, outlook autocomplete entries, shortcuts and different applications tweaks you make over the years. Loosing or resetting a clients profile causes the most headaches in any Terminal Server / VDI deployment I've encountered. Users don't care about the complexities, they just want it back and working "like they remember".
So onto profile management - with Active Directory & GPOs you can set up roaming profiles and such. You can tweak the users environment, apply custom MS Office GPOs etc but you can't get into profile in depth. You can edit the default user profile to get down and dirty but to do this for each VDI Master or TS Server can be tedious.
What the Profile Managers offer is twofold. One they have a way of centralising profiles and intelligently managing them. RTO stores the profile on a compressed format on the file share and streams it back to the user on an on demand basis - plus it only streams what's needed, say a 100 meg profile only streams 20 meg down when they log in and the rest is only sent if it's accessed or needed.
Profile Managers understand which areas of the profile are important. Office 2007 for example stores some of it's customisation is an area of the profile that is not typically saved. This layer of understanding is provided through a GUI which allows lower level techs to understand and develop the profile environment in a much easier way.
Appsense claim to be able to abstract the profile so well that you can change the underlying O/S and it can load the old profile on the new O/S and still present the users desktop the same way they remember.
The best way to check these out is to request a demo or ring up your reseller and ask for a webex demo so you can see it in action.
Hope this helps a bit!
Mike
