A couple things:
1. You do not need to pay the 15 bucks over and above the $30 to access your exchange server from the Droid. For a blackberry, yes. For an android or other smartphone, all you need is a data plan (read, the $30 plan).
2. The Droid will connect to an exchange server perfectly well. Indeed, I access my corporate email account (as well as contacts and calendar) just fine. And it CAN be set to push though it will eat through your battery a lot quicker than if you have it set to check at regular intervals (like 5, 15, or 30 minutes...depending on how urgent the messages are). HOWEVER, and here is the big issue, it DEPENDS on how your IT department has your exchange server and activesync configured. During my setup, all I needed to do was enter the server address (its the same as the OWA http address), my username (entered as domainusername), and my password. Setup activation took care of the rest.
You could try buying a droid and seeing if you can get it to easily connect with your exchange server. If it doesnt work, you could always go back to the blackberry. Heres another way to check if it will be easy to setup, though: if you anyone in your firm is using a Windows Mobile device to connect to the corporate email server, you should be fine.