Actually, I just got a G1.
I have been an Outlook devotee since 1999/2000. While in school, I used a PDA synced w/Outlook to keep a schedule. Recently, I finally got a WinMo phone (used Hermes/Trion). It was very having a converged device (and if you search my posts here, you'll see that wasn't my opinion in the past). Also, the application-base in WinMo is extensive!
Now, I love my G1! It is no-where near as mature. But, it works in the device/OS's favor, as WinMo is so tied to the tried-and-true that companies are rushing to build their own shells en masse. After using a stylus for years, I can't believe WinMo didn't go finger-friendly from the beginning.
But, as far as services/user experience.... I don't feel I have gained or lost - or rather, there are trade-offs. Google has the annoying habit of adding e.v.e.r.y.l.a.s.t.p.e.r.s.o.n you e-mail to your contact list. And GMail/Contacts isn't smart enough to recognize duplicates, so I get 2 entries for my friends' work and personal addresses However, the 'cloud' services offered by Google outweigh those by MS or any 3rd part by about a million. I haven't used Exchange, except at work, where it is hosted on site, so no delays. But, having push services is pretty nice.
Anyhow, I've converted. It was pretty easy to install Google Calendar Sync - so items I add on my phone are synced back to Outlook. I still use Outlook to POP my GMail acct, so that doesn't change anything. Thought I haven't had very may problems, being rd of ActiveSync/WMDC is not the worst thing to ever happen to a person.
Finding the applications I want to use isn' as easy as WinMo, but the ability to use a solid mobile web browser negates a lot of the special app use needed on WinMo.
I'm just waiting for more Android devices to hit the open market, so we can get the app-base there!
-bZj