I'm on a 1.5Ghz PowerBook w/ mobility 9700 thingy outfitted with 128mb video ram, and I'm running in native res (1280x864 I think). I'm not really sure whether my machine is handling it and I'd rather have smooth gameplay than crazy amazing graphics.

Thing is, changing the settings doesn't seem to make a huge difference on the FPS rating in the top corner, apart from the lighting maps thing which turns performance completely to sh** when I switch it off. The FPS also changes drastically depending on what I'm looking at in game.

Is there some repeatable benchmark I can run that'll give me hard numbers, like good old Quake timedemo2 ?

You can try typing /toggleframerategraph and look at that...

Unfortunately there isn't anything like that for VO yet. I want to do it but it's way low on the list of things to do.

The toggleframerategraph thing worked great, thanks!

I'm still somewhat disappointed with performance - is this a limitation of the hardware I've got, or just down to less optimization on the Mac client? (Which I'd totally understand - I'm amazed there's a Mac client at all!)

It's more of the unoptimized drivers in the OS.
Your hardware should run the game very well.
Turning off shaders will help a lot on the mac.

Okay, I'll dump the shaders. I'm kind of unsure what they do anyhow -- what would be a good "thing" to look at in game to compare with and without?

I listened to the gamesome Mac thing last night and it did sound like there are issues with Mac OS X that Apple are looking at. Fingers crossed for leaps and bounds in performance! ;-)

I dare you to hold your breath ;)

The stations are a good thing that shows the difference between shaders and no shaders. The Marauder, Prometheus, and Valkyrie are the only 3 ships that use shaders so they would be good to show the difference too.
Some asteroids use shaders, also.

I don't want to start a completely new thread to this, but on the FPS issue overall... I think the CPU/bus speed is also having a major impact on the FPS (I can demostrate that by changing texture settings and shaders to max and min, and the FPS doesn't vary too much on my iBook G4) ... so is there anything that could be done on the game side for the speed of geometry calculations? Could Altivec optimizations help it? Does the game have any Altivec code? (just curious...)

Of course, to look at the situation, the game plays very well on the iBook G4 with moderate settings, so the issue isn't very important.

The "timedemo" would be easy to do: just fix the same station view in the login screen (I've noticed that somehow the game looks up the last station you logged out from). Then calculating the average FPS for a couple of rotations of that station view -> voila, there's your timedemo

No, VO doesn't use any altivec instructions at this time.