[jbairdjr]

I use a similar set up at work.
Outlook checks for mail every minute, as does a re-director that we have running (not the desktop re-director).
I have both leave messages on the server. Outlook is set up to delete messages from the server when I empty the Deleted Items folder.
I like getting the messages in both places, as I have accidently deleted messages from my Blackberry or Outlook on more than one occasion.
As far as spam goes, try directing the mail to a gmail account. It has the best spam filter I have seen, and you can have GMAIL re-direct the mail to the blackberry. I do this with my home and work accounts, and I get my mail almost immediately. Before I was waiting 10 minutes or so for my home email.