Tested.com has a nice rundown of all the different button layouts and a discussion on what might constitute the best layout. One of the comments goes on to say:
I have the Droid 1 and my girlfriend has the Droid 2. The back button and menu button are switched on the two phones. Every single time she tries to use my phone she ends up exiting a program by accident for this reason.
Lots of people call me an Android hater. I have my reasons. Chief among them is Google’s utter disrespect for consistency and user experience.
Here I have a composite image of Google’s new “flagship” Nexus S (top) and the Samsung Galaxy on which the Nexus is based. Notice anything different?
I’ll help you out: every single hardware button is in a different place. Every. Single. Button.
But hey guess what! The Nexus S has Near Field Communications! NFC! You can use it right now for all sorts of cool stuff like … ummm … actually no, it’s of no use whatsoever.