This only appears to happen on Macs with shaders on, I tried it on a few other setups and none of them exhibited this behavior.
Machine: G5 2GHz Rev. A (Edit: typo) 512MB + AGP 8x ATY Radeon 9600 64MB
Quality: EVERYTHING is set to maximum, except distance LOD (0.7) and texture quality (High). Reducing quality does not affect this behavior.
Behavior: All stations except for the first one (and sometimes second, or even third) to load during a VO session (not counting the menu station, for some reason) lag HORRIDLY.

When I first went to Geira Rutilus O4 "Geira Watch," merely looking at the station sent my computer into a seizure. (framerate dropped below 2fps) However, when I quit VO, took a pizza break, and returned, the station did not lag. At all. Now every other station lags. Repeating the quit/login behavior de-lags that station, but lags the others. What's going on?
-:sigma.SB

I don't think this is a "Mac" problem but perhaps a video/settings problem. I have run VO under both 10.3 and 10.4 and never experienced such behavior, but I'm using a nVidia 6800 Ultra and perhaps it does a better job.

Have you played with video settings to see if less than maximum settings would help?

Also, I would consider 256MB RAM on a G5 to be the absolute minimum, especially for something like VO. You could be running into virtual memory lags.

I have a very similar problem. I just reported it as a bug. The Stations lag a lot when I have shaders on. If it is off it is no problem. Even when the resolution is low. I have an iMac G5 with a 1Gb of ram and 64mb Nvidia FX5200 Ultra. I know it is a weak card but it seems inconsistent. Sometimes it runs super good... then blah!

objectifier:
> Have you played with video settings to see if less than maximum settings would help?
Solra Bizna:
> Quality: EVERYTHING is set to maximum, [snip]. Reducing quality does not affect this behavior.

objectifier:
> I would consider 256MB RAM on a G5 to be the absolute minimum
Sorry, the 256 was a typo. All of my other beefy machines have 256.
It's not VM lag, VO's usage doesn't even approach 256MB last I checked.

This would appear to only happen on cards with 64MB or less of memory, possibly the VOBs for the stations are being mismanaged in some way? I will try playing with VOBs off and see.
-:sigma.SB

From an interview with John Bergman:

Our recommended system requirements are a 2 GHz PC (or G5 Mac) with 512 MB of RAM and a GeForce FX5600 / Radeon 9600 or better.

I would recommend trying to lower the texture resolution by another notch. 64meg cards may not have enough memory to handle everything and we don't free textures once you see them. Mac OS X has a really big problem with texture swapping/thrashing and I think this is what the problem is.
On second thought, maybe the drivers don't like the way I'm using vertex buffers.

dovertexbuffers=0
doindexbuffers=0
do_compiled_vertex_array=0
Suddenly the lag stops. Solid 100fps with vsync override on on a 100Hz monitor. Aren't object buffers supposed to speed this sort of thing up?
Looks like OSX's texture thrashing issues extend to other VRAM-resident resources as well...
-:sigma.SB

100 fps??? i only see that during the loading screen! :)

i usually see 50fps at most when flying through an empty system with few asteroids. i believe 20fps is my average.... poor old mac. :)

Solra, what is vsync override?

I too have experienced this problem. At first, it seemed to effect many stations.
after 1.1.5, fewer stations were a problem. Bumping all settings up to maximum (!)
resulted in even fewer problems, and the probs experienced became intermittant.
That is to say: I enter a sector with the station in view and get about 3fps or so.
BUT, after docking at station and leaving, I am suddenly getting 100-120fps looking
at the station! I have noticed similar happenings by leaving the sector and re-entering. After updating to OSX 10.3.7 (and the new 1.1.6) there has been more
(if somewhat slighter) improvement.