Traded in my Nokia E65 for the Samsung Omnia2 (GT-I8000) on Christmas day 2009. Switched to M1 from Singtel.
Original contract price: $398
SunSaver Plus discount: -$100
Data Plan discount: -$100
Switching from Singtel: -$100
E65 Trade-in: -$100
Final amount paid for handset: $0.
Still getting used to the phone and applying numerous registry hacks. It's not all that bad actually ... getting an iPhone just ties you in to a fixed user experience. I still prefer some flexibility and the ability to get under the hood.
I'm quite sure you can get under the hood for the iPhone and Andriod phones as well. And I agree: Windows Mobile is slow and laggy, but somehow, only on Samsung handsets. HTC phones with lesser hardware specs seem to run circles around my Omnia2. Sigh.