I use it everyday! I work at WICKSoft, and we do almost everything from our BlackBerrys.
The shared calendars and contacts portion is especially useful now that editing is supported. Before it was 'view only', but now that you can create and edit appointments and contacts, and I use it a lot to schedule presentations and update master contact lists.
The file access component (being able to view and email files on my W: or S: drive) has always been a big one for me, especially as I travel quite a bit. I honestly do not understand how people can live without access to their files. I can't count the number of times that I've had to get an updated PPT or Excel file when away from the office.
I also use it find old email messages that are no longer stored on my BlackBerry-- there are many times where I've sent an email to someone but don't have a copy on my phone, so I use WICKSoft to search a mailbox.
Will