Okay people, good news. I hijacked my GF's MacBook, and restored Portal 2 from my backup from Steam and loaded it up.
Late 09 Unibody White MacBook
Intel Core2Duo 2.26Ghz
nVidia 9400m
2GB RAM
Mac OSX 10.6.7
First, it works! No issues loading it up. I played in OSX 10.6.7 as listed. I cannot and will not be doing BootCamp for the 9400m. My GF doesn't use Windows and there's no way I'm installing Windows just to test this... sorry but just gonna throw that out there.
Second, you'll want to play on all lows, low everything, shaders, details, textures, texture filtering all that jazz, no AA.
Now, for resolution, I tested it on all four possible 16:10 resolutions, ranging form 800x500 up to native 1280x800. Basically at native resolution you'll average around 24-26FPS. I "tested" I say that because it was simply ONE ROOM I ran around in, didn't bother with much else. Start of Chapter 2, I had access to the portal gun with both orange/blue. Anyway, when you look into a portal, like go up to it, I noticed this is where FPS usually dips. It drops to about 16-17FPS when you just stare through. Still not choppy but not close to 30FPS.
So I tested the lowest res 800x500, FPS of course goes up, 30-35 but still dips into 20's. Problem is, 800x500 looks a bit, pixelated. Kind of nasty looking, playable but meh.
So the next resolution up, I forget was like 1024x640 or something? This looks a LOT better visually. Text isn't distorted, things are more smoothed out. Avg high 20's into 30's and dips into low 20's when looking into a portal. Not bad. Game still looks good.
One more res up wasn't bad either, right below native resolution. Got slight worse frame rates than lower resolution and looked just as good.
My recommendation is probably 1024x640 full screened. It looks clean and runs the best. You can definitely play at native resolution, I didn't get a slideshow or anything. If I didn't have the FPS counter up I probably wouldn't have thought too much of it to be honest. Plays well. If this was the only option I had to play Portal 2, I wouldn't hesitate to get it. Now remember BootCamp *should* run this even better as that's always seemed to be the case when it came to OSX vs BootCamp gaming performance.
So basically if the 9400m can run it, anything better than the 9400m SHOULD be able to run Portal 2, given you're fine with lower settings and resolution. This confirms my thoughts that the 320m will be totally FINE when running this game, as well as the HD 3000. I am not too familiar with the x1600 so I cannot comment on that. I doubt the older GMA950 and x3100 will work though lol Guessing the 9400m is the end of the line here folks when it comes to Source gaming.
Anyway, I am uploading a 5min youtube movie I made testing out the various resolutions on the 9400m machine. Like I said it's not much, just in a single level, with a laser going though =D and with the portal gun to get the more intense graphical effects working. I'll link when that's up. My DSL uploads are TERRIBLE, so please give me a couple hours before I report back.
Happy gaming!
*EDIT*
UPLOADED hope this helps some people.
white Macbook late 09 9400m Portal 2