corporate sync does NOT work properly on D2G/Pro/...
Yes, you might be lucky or it may be because of your settings, but on the Moto Forums most people experience only initial success with both of those, and then push eventually fails.My office doesn't use the most advanced of Exchange servers (no pin, no ssl...) but, I have had great luck with two workarounds.
The first, and easiest, is Improved Email from the market, it's free, it looks like the AOSP email program, and push seems to work fine. Does not have a manual setup option.
The second, grab Email.apk from a Cyanogen ROM and install it. It might require you to push it to /system/app and set its permissions (which requires root). It allows for manual setup.
Again, our exchange server is not the most secure so if the security settings are causing some of the push issues, these workarounds may not help you.
Not that anyone asked, but there's my $0.02.
Robert, are you using push notification or you are polling every 15 mins (the default setting)? For me polling always worked fine (I am on exchange 2007). Push is what is intermittent.