A friend of mine has an iMac G4 1Ghz 17inch, bought in march 2003 (almost like yours). He has 512mb ram and the Geforce4 mx (64mb I think).
Panther is running on his iMac for few days and as far as I got everything, he is more than just happy with it. He is even using the fast user switch to switch between desktops (work area, private area).. I found it quite funny in the beginning (one user two accounts) but now it looks kinda useful to me