Sure have, Mak's on the team now
He will use the browser he wishes to use, some people don't like Firefox (including myself) becuase of all the add-ons that come with it. Some however like this and think that browsers without add-on features are rubbish. Others prefer Opera becuase they find it more stable and like its "out of the box" setup.
It's all down to personal taste. In future you could reccomend Firefox as an alternate browser choice and provide a download link.
This then allows the user to find out more infomation if they wish / or read the other replies and attempt to fix the existing problem.
Cheers,
~ Tkey