Since the first appearance of the Windows Phone 7 in the Netherlands I am the proud owner of a HTC Trophy. After that I bought a Samsung Omnia 7 and just a few months ago a Nokia Lumia 800.
The biggest difference between the three. The Samsung has the biggest screen. Although it is also a amoled it looks lighter then the Nokia. The pictures does not make it complete clear, but there is a difference in colors between them. Samsung and Nokia are close.
For now I like the Nokia more then the others. The Samsung has a better screen then the HTC, but is slightly bigger. Although the difference in size between the Samsung and Nokia is very minimal, the Samsung feels bigger.
I have used Windows Mobile, Android and iPhone, but Windows Phone 7 integrates way better with Exchange, Office 365 and Skydrive. I love it.