I think I would trust Google Checkout more than Paypal but that's highly biased based on how much spam there is for paypal and sometimes paypal is thought of as a cheap-n-easy solution for companies that aren't big or reliable enough to have a `proper` checkout system.
probably why alot of small 'shops' have popped up over ebay
instead of bidding for something they just have 'buy now for $xx.xx'
some people just dont have the time or know how to set up a shopping cart of their own and ebay does the rest for them
i know you can buy off the shelf programs but as ecommerce is still new punters are still wary of sites theyve never heard of even if they are selling products that they have