Well, I didn't know about IE9 being available
.. until I read about it here in the Reg, as thy were going on about download numbers compared to Mozilla's download numbers. I know about Firefox4 being released, because Mozilla's spending their millions on making sure everyone knows. AND because every time a new beta came out, the reg was quick to point it out.
I installed betas of both back in September. but I'd not really used them much in recent months (Opera11 and Chrome are much faster). So end of last week, I decided to benchmark them. I even managed to benchmark the betas against them. It was a little bit of a struggle to find the final release of IE9 in fact (if you went to the download site using hte beta, it assumed you had the final). Meanwhile, I restarted Firefox4 beta7 after doing the benchmarks to go look at the IE site, and it had magically upgraded for me, without even asking.
So by 'widely available' perhaps they're talking about mass downloads. If you have the IE9 beta, you can't get the full. If you have the Firefox4 beta, you are almost forced into getting the full. It's two different approaches, that maybe reflect the differing download totals.
After I did those two main browsers, I then went on and did a bunch of others, some old ones for reference, and then every client on the Browserchoice.eu page