What would I be missing?

I am a former BB BES user who has been limping along with Android for several months. We brought our Exchange server in house...but did want to shell out the $$ for BES. I have since learned about BESx and I am now considering this.

My question...what would I give up just doing IMAP4 from our Exchange server? All emails would push...calendars would sync because the appts come through as an email (learned this a couple days ago)...the only thing I appear to be missing would be wireless contact sync? I know I will lose many IT policies that I never used before when we did hosted exhange/BES. I am also embarrassed to say that I didn't even know that BB Desktop manager backed up the BB!! I thought only people who didn't have BES needed desktop manager.