https://market.android.com/details?id=com.nitrodesk.droid20.nitroid

The UI is *terrible*, and it seemed to suck up more battery than I was willing to accept, but it did seem to sync everything properly in the brief time I used the trial. If you *must* have proper sync, it's probably as good as it gets right now.

Fortunately, the K-9 email developers are working on Excahnge activesync support. Given how solid K-9 is as a client, I'd keep an eye on that.