Gecko, like every other Open Source project, is getting smaller and faster with every release. This is the nature of OS development, and I love it.
Look, compare Firefox, Mozilla Suite, Open Office, KDE, Gnome, Kernel, etc. Every piece gets faster with every release. If not faster, than it stays in 0 point, if it’ll regress in performance, it’ll get faster than before in the next one, because automated performance systems will catch the rise and someone will investigate that part of the code, cleaning it, and optimizing.
For Mozilla, you can look at build-graphs.mozilla.org and compare the results in, say 360 days.
Of course, it doesn’t mean that OS is faster than proprietary software everywhere. There are many other issues that can make it opposite, but comparing two pieces of software requires much more than simple timer. For example comparing browsers performance is very hard. IE will start with the OS, Opera is pure browser, while Firefox is Gecko and Gecko is full cross-platform RAD environment. Which one is faster, depends on the test and everything might make the difference, so, to make a precise statement about performance, you need very complex term. Like “App X in ver Z is faster than Y in ver U on Linux, in loading code V when not using cache”, so I think that this kind of comparison is more a journalist job (who can say “App X is reaaally fast” and noone will force them to prove their claims), but for us, most important is to compare our versions, make sure that every next is faster and seek&destroy issues that hits the default user hardest. (it doesn’t apply to pre 1.0 versions. Yes, Flock will have to be optimized before 1.0 ;)).