The clincher for me was looking at Chrome extension development. The extension system for Chrome seems really accessible and well thought out and I feel like I could make some Chrome extensions for myself without really any hassle at all. In contrast, I have been told by acquaintances who have made FF add-ons that FF add-on development can be quite an unpleasant experience.
Coming from FF I had this funny moment when I opened up the Chrome preferences menu and it opened in a tab, just like a web page (I assume because it is just a web page) and I thought "huh, that feels a little strange..." then I opened up some extension's options page and it was just a web page too and I thought "Actually, preferences and options as just plain web pages is really cool and intuitive after getting over the subtle shock of them not being in those little pop-up dialogs." It unifies things nicely and this approach is one of the reasons why extension development in Chrome can be made so intuitive for people already experienced with web technologies.
Regarding the slow performance of FF lately: I remember some months ago I had this situation where I was trying to debug a JS powered upload progress bar I was working on which relied on AJAX calls to update the length of the bar and it just wasn't updating or it would update once, then nothing until the very end when it would shoot to 100%. Watching in Firebug, AJAX calls were being made but seemingly nothing was coming back. I was stumped, I tried everything I could think of, until by chance I tried turning Firebug off and bam! My upload progress bar started working perfectly. JS in Firefox with Firebug on top of it was slow enough that the multiple AJAX calls needed by the upload progress bar weren't working properly anymore. Looking back, I think that day the seed was planted for my move to Chrome.
Firecookie http://www.softwareishard.com/blog/firecookie/
Firequery http://firequery.binaryage.com/
Firepicker http://thedarkone.github.com/firepicker/
Jsonview http://jsonview.com/
Colorzilla http://www.colorzilla.com/firefox/
Built into the Webkit Developer Tools
> Firequery http://firequery.binaryage.com/
jQuery objects visualisation (in console and inspector) are in the Developer Tools, rest is not (though the injection is a bookmarklet/browser extension away)
> Firepicker http://thedarkone.github.com/firepicker/
Missing indeed, Opera's Dragonfly has a color picker but the webkit devtools don't.
> Jsonview http://jsonview.com/
https://chrome.google.com/webstore/detail/chklaanhfefbnpoihc...
https://chrome.google.com/webstore/detail/ddngkjbldiejbheifc...
https://github.com/rfletcher/safari-json-formatter
> Colorzilla http://www.colorzilla.com/firefox/
https://chrome.google.com/webstore/detail/hmdcmlfkchdmnmnmhe... ?
On an unrelated note I can't live without tree style tabs(On average I have 30+ open tabs, which is unmanageable in chrome, hangs some time) and vimperator. All in all I still prefer firefox.