John M - no shots in the arm - yet.
When you use Method more often, it stays fast since the pages stay "warm". If you only hit Method occasionally, it has to load more libraries again from scratch. So, I'm not sure if maybe before you weren't getting in every day.
We also had to replace a key hardware component on the servers on Sunday night / early Monday morning (see Danny's twitter post on www.twitter.com/followmethod). That might have helped.
We are constantly tweaking and improving the back-end of Method. So each month it becomes faster, stronger and smarter than the previous month. But this month's big update hasn't come out yet! That's planned for later today.
FireFox 4 - we use *a lot* of javascript. FireFox 4 has an improved javascript engine, so, yes, that could have a lot to do with it.
In fact, today's update is a big one because it announces compatibility for other browsers with improved javascript engines, such as Internet Explorer 9, Google Chrome and Safari. So, after the initial download of new libraries today, you should see Method get some further performance shots in the arm. :)
Paul