Thanks - it is something I will have to consider... The .5% conversion rate is probably a bit high in my case - but you are right - If I was making $50 on each conversion rather than like $1 for firefox with the google toolbar - it would be certainly be worth considering!
(particularly now that it is so easy to set up a google checkout shopping cart :-
Getting started with the Google Checkout shopping cart - Google Checkout Developers Forum | Google Groups