Nothing really, I have a HTC Hero that I only got 2ish months ago and works well.
True the tech on the phone can be found on other phones but this is the first time I have seen most if not all the tech I wanted on one device, its 1ghz processor (Snapdragon processor) and 512Mb RAM, I suppose being the main two.
I used the iPhone 2g then the 3G, moving to HTC Hero few months back, I just can’t believe how much I love the simple thing of multitasking. My Hero can get a bit slow when i have Twitter running, MSN, email... 24/7, turn the satnav on and you find it’s a bit slow on telling me to turn.
Also the price was good (off contract).
I would not say to everyone to go out and get one. Well, simply i don’t want to have a phone everyone has :p
Having got the iPhone shipped to me on day of UK launch, I would guess I’m just a so called "early adopter" to. :)