I found this information pretty useful. I got mine to work and then it just suddenly stopped working:
1. I connected everything up like you described and my pineapple itself had internet access to install modules with. From the WAN port to the mac's ethernet. If I connected to the pineapple's SSID then I did not have internet access at all.
2. I installed the network manager infusion and then set the ICS the way you described: from eth1 to wlan0.
3. I tested this with my cell phone and it was snared by karma when trying to connect to an access point and voila! i could load up webpages with it. Well, webpage, just once. After that I could not load anything else. I also was no longer able to connect to the pineapple from my mac via 192.168.2.2 any longer, it could not be pinged either.
4. Since I had the network manager installed now I tried to switch the ICS to the br-lan as you said that it was required in "some cases". This did not resolve things either.
Since then I have been completely unable to get this thing back to taking on 192.168.2.2
Do you know what this can mean or should I dump in more info?