To BenPS3, the iPhone 4 screen is brighter and clearer, fact, go turn the screens to full brightness on the same picture and you'll see it looks much better on the iPhone 4 as the iPhone 4 uses IPS technology and has the best screen resolution for a phone on the market so the highest pixel density.
The Desire HD is an awesome phone thanks to Android 2.2 but I find it a little bit too big.
It feels good and shows a solid build but I would have hoped the screen would be AMOLED like on the old Desire.
It false to call this HD but it should be called XL as it's the exact same as Desire, the 8MP camera is not better than the 5MP on the Desire which does HD 720p recording too. The old desire uses AMOLED too so you get pure blacks and pure whites and has a smaller screen but same resolution so you get a higher pixel density.
If i was you, I'd check out the Samsung Galaxy S, it has the fastest graphics processor of any Android phone on the market, AMOLED, it can take screenshots without rooting and is more Android as the HTC Desire HD as HTC Sense UI.
If I was you, I'd save your money and get a Desire or Galaxy S but the Desire HD does feel the best in your hand.
Battery life is ok, will last around 3 days on standby with 2 hours of web usage.
In my opinion, the Samsung Galaxy S is by far the superior Android.
It would have been 5* it had a higher capacity battery, AMOLED display, the Galaxy S graphics chip and a higher resolution display otherwise I see no point in getting this over the Desire other than for the 4.3" screen