Probably your first question you need to ask yourself is.....
Do you want to stay with a UI overlayed smartphone like a Sense or Touch Wiz, etc. phone or are you willing to go Pure Google in that case you have one choice the Galaxy Nexus.
I only say this because whatever device you purchase I would assume you would be going after something that is promised to update to Android 4.x (Ice Cream Sandwich). I would make sure of this, being locked in for 1 or 2 yrs on a new phone you don't want to miss out on something not getting ICS.