If you are wanting a good device for your corporate exchange mail, then I would not purchase the droid as it has known issues with this. After the latest update, 2.0.1, Exchange accounts are repeatedly being deleted from the device. You may want to stick with a windows mobile device like the TP2, or a Blackberry device. I have the droid and my wife has the TP2 and she loves it.
The Droid does support Exchange ActiveSync, but not some ActiveSync policies (these are rules set on the Exchange server by your IT department to enhance security). Unfortately setting policies is pretty much an industry-standard practice, so it makes things complicated. I for one was able to sync my Exchange calendar and contacts just fine on a Droid with the 2.0 (e.g. original) software. Although I wasn't able to get email working, I was able to work around that by setting up email via IMAP instead of Exchange (it's generally faster anyway in my experience). However this morning 2.0.1 was released and it appears to have broken my ability to get the calendar and contacts to sync. =/
If you're interested in better Exchange/ActiveSync on the Droid or other Android-powered devices, I suggest that you go here and start the bug that requests better ActiveSync policy support:
Word around the IT department at my office is that this is gaining momentum and may be fixed in Q2 of calendar year 2010, but the more people demanding it the more likely it is to be supported.
Regarding the apparent breakage in the 2.0.1 software that I mentioned, I'd also suggest starring this bug: