If the HTC Desire is anything to go by then it will be a fucking fantastic phone. I refused to join the crowd and PAY for an iPhone 4 when I was able to get an HTC Desire for nowt, pay less per month on my contract AND have a shorter contract (thank you very much Vodafone retainment team!).
The major achilles heel of the Desire though is the battery life (though you can get power saving apps to help get round that) and the Desire HD is going to have more processing power and more functionality but run EXACTLY the same battery meaning it's going to be even more of an issue!