You certainly have!
Welcome to the Android Forums.
I haven't got the Desire but, have moved to Android (X10) from the iPhone after just 6 months. My partner on the other hand, did move from the iPhone 3GS to the Desire and loves it! Won't use it properly till we have a case for it though and was hard pushed to touch it without a screen protector on lol. Thankfully we were on PAYG though, so again, only 6 months with the iPhone and again, PAYG on the Desire (i went contract :s, possibly so i cant have another phone in another 6 months).
Got any apps downloaded yet? If you're into emulators, I strongly suggest using them on Android. The GBA emulator on the Desire is far superior to the one I tried on the iPhone, jailbroken.