Indeed! Due the performance issues when "extending" the wireless network, I simply have my Airport Express "Join" my wireless network. This works great, even with non-Apple routers.
For more details about extending a Wi-Fi network, take a look at this:
http://support.apple.com/kb/HT4145
Apple says, in part, "Adding Wi-Fi base stations when it is unnecessary can reduce Wi-Fi throughput because the Wi-Fi network will require more data management overhead. The network configuration also becomes more complex. In the case of a wirelessly extended network, throughput may be reduced to less than 60 percent of that of a single device. The general rule is to keep the Wi-Fi network as simple as possible. You can accomplish this by using the minimum number of Wi-Fi base stations required to service the physical network area and by using Ethernet wherever possible."
Enjoy,
Jim