Android Button Comparison
This is a comparison of hardware buttons on many popular Android devices. I know this isn't all of them but I think it's filled out enough.
I find it interesting that series of devices (e.g. Droid Series) don't match. Also, there is no consistency in regards to icon design on each device.
UPDATE: The Bergol says I have used the incorrect Droid 2 in this list. Instead of matching the Droid, it matches the Droid Pro. I apologize for my mistake.
UPDATE 2: Thanks for all the views. This was originally pointed out by Ben but John Gruber from Daring Fireball was my source. Engadget has created a better version here. I meant no disrespect to the Android community but feel that muscle memory can cause a frustrating experience when changing devices.