i for one love the iMac keyboard, in fact i'm using the wireless version right now. i feel the quality is better than that of the windows keyboards.
if you have sufficient funds, the logitech dinovo keyboard/mouse combo's are nice. unfortunately, you cannot purchase each independantly. it's definitely important to try out a keyboard before purchase if you can.
also, if you get a windows keyboard, you will have to live with a somewhat different and sometimes confuzzling arrangement of keys.
S