This isn't really a problem, more of an annoyance...
I'm currently using a Belkin FSD8053 v1011uk with Ralink D2870USB kext from their site. I have also tried with aquamac's airport mod of the same kext. Looks nicer but same issue.
It is connecting as normal, but at around 50% of its speed.
On my HP Compaq DC7100 (yes, the same P.O.S that all colleges, schools and almost everybody else uses in the office or in a call centre) I get around 600k max download speed. The same dongle on the same machine in Ubuntu or Win XP gets around 1300k max d/l, torrents, ftp, anything. Also, other machines connected to same router (N or G, no difference) will get around 1300k.
Ralink Wireless Utility shows excellent connection.
Any ideas? My first thought was a USB speed issue, but I'm not too clued up on it and still need to test another USB device like a memory pen or external HDD for transfer speed on different OS's.
BTW, installed using iAtkos S3 and tried on 10.6.3 and again after updating to 10.6.7 and 10.6.8, same issue. Also, ethernet can still get the correct speed, but i want to avoid the purchase of a 50 foot CAT5 cable...