I just bought a Nexus One for work (through my Android Developer account), and when I turned it on I immediately noticed that something was wrong. It was different from my own Nexus One. One thing I really like about the N1 is the AMOLED display. Contrast is incredibly good and black is truly black, not grey. In the end of July HTC decided to change the hardware on both Desire and Nexus One, and so the new unit I bought through work does not have an AMOLED display but a rather boring"Super LCD" instead. Here's a couple of pics.

The two phones next to each other. The trackballs look different as well.

A macro shot of the non-OLED device

Macro shot of the OLED device.