Why I'm not likely to use Chrome much in the future
I'll start with the story. For a while now, support for mouse gestures has been an important part of browsing for me. In Firefox I currently use FireGestures while in Chrome I used to use something called Smooth Gestures. Smooth Gestures started out as the same sort of completely free extension as FireGestures. After a while it grew a couple of sorts of ads that defaulted to on (and got reset that way periodically) but could be turned off if you wanted (in a typical move, you got a vague guilt trip about turning them off). Recently the developer of Smooth Gestures used Chrome's mandatory auto-update mechanism for extensions to push out an update that quietly makes some of the ads mandatory unless you pay for the extension. I uninstalled Smooth Gestures as soon as I found this out, as have quite a lot of people, and then I went looking for a replacement. What I found (especially among high ranked, apparently functional gestures extensions) is almost entirely things like Smooth Gestures or worse (one explicitly harvests theoretically anonymous information about your browsing, for example).
While the lack of gestures provides a good reason to not be fond of Chrome, that's not really why I now feel uninterested in it. The real problem is that this is the sign of a drastic difference in the culture of extensions between Chrome and Firefox, one that is very much not in Chrome's favour. To simplify things, Firefox started with a genuine FOSS extensions culture and as far as I can tell has mostly retained that. I don't know if you can charge for extensions now, but for a long time you couldn't and a great many highly used and core extensions are fully free and open source. By contrast, Chrome sure seems to have what I will call an 'app store' culture of extensions. You get Chrome extensions through the 'Chrome Web Shop', for example, and as we've seen many of them are no more free than the 'free' apps in the iOS and Android app stores. The behavior of the Smooth Gestures developers is perfectly in line with the norms of app store culture.
What this means to me is that I can't trust Chrome extensions any more. Even if I carefully inspect the documentation for an extension and it isn't lying about being harmless today, the mandatory silent auto-updates of extensions can change that tomorrow if the developer wants and the Chrome extension culture clearly condones and even possibly approves of this. I rather expect that to a lot of Chrome extension developers I am a resource to be monetized not someone to be respected. Given Google's general behavior I can't count on them policing this even if I thought they were interested in doing so, and I don't think they are (to put it one way, people who run a 'Web Shop' do not make money from refusing to list things in their shop).
I won't pretend that Firefox is immune from an individual extension trying to sneak something evil in (although I believe Mozilla has some sort of auditing procedure). However I fundamentally trust the Mozilla people to be on my side in a way that I don't for Chrome. I'm pretty sure that if any equally popular Firefox extension tried to pull what Smooth Gestures did there would have been a huge uproar and they might well have been thrown off addons.mozilla.org for misleading and sleazy behavior, either immediately or in response to community pressure. And pragmatically I think the culture of Firefox extension developers is such that people who would do this sort of stuff don't develop extensions for Firefox in the first place.
I still have a couple of Chrome extensions left and I'll probably keep them around. But my use of Chrome is now going to pretty much be only for my Chrome Incognito hack.