In this part I'm just going to touch some points which I thought should be good to mentioned
I really like Nokia's Address book as I can put in hell a lot of information into the contact card. But the good thing about the Android Address book is that its synced with my Google contacts and Facebook. But Google contact have has another issue of not being connected to the contact's Google profile and the contact information published there. More on that later. Google and Android contacts also ignore nicknames while searching.
N900 has the best camera among the three
All three phones show SMS as conversation. I like how N900 shows the conversations and the the friendly language used. iPhone has a funny talk bubble and a confusing interface and Android has tech language used like "Delete Thread". What thread boss?
I would love to have an option from a contact card to see my text conversation and call history with him/her. I think its pretty easy and possible to do this on Android.
I really like the Android notification screen which can be swiped down from the header which lists out all the notifications for me. Very nicely done.
Home screen widgets
iPhone doesn't allow home screen widgets which is a very bad thing. N900 has it but its Nexus which takes the cake here. There are lots of useful home screen widgets in the Android Market which ranges from just switches of many of the mostly used functionalities to snapshots of your Calendar/Facebook etc.
All three phones use modal windows to show contextual menu/keyboard but Nexus has the most unintuitive way of dismissing them. When iPhone and N900 closes modal windows if I tap on the background, Nexus makes me hit the back button to do this. This is bad interaction design.
One hand usage
N900 cant be used with one hand coz of its fixed landscape mode (Utter Fail). One hand usage is a challenge even on Nexus coz of its poor touch response. iPhone scores hands down here :)
iPhone scores on the smallest aspects which others tend to ignore. But I think if Android gives more importance to iron out the small issues it will win in the long run. Android has all the potential to be a Geek's favorite phone.
Phew I think I'm done :)