But in the same time they both kept eroding IE's market share, so overall Firefox grew by getting some IE users, and losing a few to Chrome, while Chrome grew from both IE and Firefox.
I think it's a pretty win-win situation for both, at least for now. Together they are big enough to standardize some features, even without Microsoft's support (like say WebM, WebGL, or Native Client). So, I think that's good.
On a side note, I think something like 40-50% of Techcrunch readers are using Chrome, and that's a pretty good indication to where Chrome is going, just like it used to be for Firefox, when it had only 10-15% overall marketshare, but around 25-30% on tech sites. And now has caught up to that.
Also I'm not sure early adopters is a good description, Firefox users are more likely to care about usability, security, privacy, extensions that aren't possible with Chrome or that Google considers not important or don't want it (something like NoScript or RefControl) and open source (which Chrome is not, sure Chromium is but the distinction is important because of real world implications and other reasons). These things do tend to be more important for some early adopters, I'm not sure I'd grant "technical proficiency" to mere "tech enthusiast".
See http://gs.statcounter.com/#browser-ww-monthly-200911-201105
But it does raise a question, since they count browser usage, and not unique users -- I fully expect that ppl who use Chrome/FF to spend a LOT more time on the web browsing more sites. If we count unique users do we see a sharp uptick in IE percentage?
[1] http://gs.statcounter.com/#browser-ww-monthly-200905-201105