Lots of these are nice points but how did I miss the emulation tools in Chrome, this article was worth the entire read and more just for that, stunningly useful! (I already use the similar thing in Firefox).
EDIT: Having played with it this is fantastic, been able to lock an emulation to the developer tools makes flipping back and forth vastly easier.
Point taken on reminding devs to break out of the popular WebKit + OSX environment to do IE, but seriously, no one is using Windows Mobile. I can't find any record of it coming in above 1% of any major browser stat reports. Total waste of time.
EDIT: Having played with it this is fantastic, been able to lock an emulation to the developer tools makes flipping back and forth vastly easier.