Hold the phone there tipdrill. Thats a very blanket statement to make. The iMac *should* work with your router.
Definitely get your iMac. Chances are it will be fine.
However, im currently experiencing major issues with my brand new 24" iMac and its built-in wireless card. It could be the mac, it could be the router. Im still trying to get to the bottom of it.
Ive tried it with a Netgear DG834G router and a Fujitsu-Siemens AP-600RP-USB router. Im having the same issue with both routers. Connects fine, but speed and signal strength are very erratic. Both routers work problem-free with my Powerbook G4, an Acer laptop and the 24" iMac if I use my Belkin USB dongle.
It might be worth hanging around and seeing if anyone who is actually using the same router as you is able to verify its abilities. You could also try asking Apple or Buffalo tech support if theyve tested it.