I have the HD2 also. Love the phone, but as it is new, I am lucky to get 1-2 days out of the battery My wife has the 3Gs and will most likely upgrade to 4 once her contract is up. Again though, she normally only gets 2-3 days out of her battery. Less with Wifi or bluetooth enabled.

iPhones would win as far as availability of apps goes. I was reading somewhere that Andriod has a higher market share over iPhone (i think it was 18% vs 14%), but there are more apps available on iPhone than Android (i think it was 240,000 vs 100,000) - At the moment anyway.

Although, you would probably find the amount of apps means shit all compared to the amount of USEFUL apps. I dont care about "fart detector" and "ghost in the picture" apps, I only care about apps like iTunes remote control, mapping / GPS software etc.

My advice, try to find people with the 2-3 phones you are looking at and have a play. See what useful apps they have, what they cost, then make up your own mind.

I think you will be happy with either the iPhone OR Android based smart phones. I think the main point is one you have gone to a smart phone, its impossible to go back.