I have an Airport Express connected to internet via an ADSL2 modem and PPOE. I used to have up to 1,8 Mb/s during downloading files.
Recently, I made the firmware uptade 7.6.3, and since I can'h have more than 1,0 Mb/s.
Than, as I saw there were problems with 7.6.3, I re-installed former firmware 7.6.2 (this is the one proposed by Airport Utility). I thought that doing that I will come back to the former configuration, and get again my former 1,8 Mb/s. And bad suprise, no. I get stuck to 1,0 Mb/s.