I've got 400MHz, so speed is an issue (2003 Britannica has this annoying 'slider' at the right which will slide in/out at a snail's pace if clicked accidentally). Search speed is also less than impressive.

Britannica has this 'root window' thing and lacks proper menus, respect for the Dock &c. That's well beyond acceptable. (It's like suggesting that, say, vi or KMail are Mac apps. They may run on a Mac, but they are not Mac applications.) It also spawns all those little sub windows with the widgets on the wrong side (which I find irritating every single times. Window close buttons have been at the top left since, forever, I guess.

Perhaps a few things have been improved since 2003, but your screenshot doesn't exactly look like that. So I am not inclined to upgrade. I find this trend particularly sad, as in the very early days of CD based encyclopaediae, Britannica had a really plain and simple multi-platform offering that made the full content available through a web browser. They didn't have 'multimedia' stuff, but even today Britannica doesn't seem to be en par with other offerings as far as non-text content is concerned. So it looks like a step backwards.

I seem to have Britannica 2003. How much is the speed increase? What about the content, by the way? The last time I used Britannica was when on the train with my South African friend around the new year. There is no Google on trains and I wanted to show him where we are going on a map. I found the quality and usability of maps on the computerised Britannica rather disappointing, though. Having used the proper Britannica atlas, I know that they have much better material than what is offered in the electronic version. Simply not quitting Britannica may be an option if you use it regularly. But as it seems to be a Java rather than a proper Mac application it seems to be quite a memory hog as well. (This also accounts for its ugliness and ignorance of HIG, I suppose.)