Paul, you heard wrong. Apple seems to build more standards-compliant hardware than just about anyone else, and their wireless networking stuff is no exception. AirPort Express cards are not only complaint, they are very good at their job, too. You can use them with ANY 802.11 b and/or g hardware.
The only issues you may encounter are dealing with the fact that Apple uses non-standard terminology in some cases. A "network name" to Apple is an SSID to everyone else, and so on. It's no biggie and you'll figure it out pretty quickly if you just read the instructions with a new router. Otherwise, post any questions you have and we'll give you a translation.