I'm using Google Checkout as well, and to be honest I'm on the fence about using it as the only option. I've tried using it as the only option but I keep getting customers emailing asking to pay with paypal.

Frustrating to say the least is the fact that google checkout prides itself on bypassing Zen Cart's create an account feature. This means that the customer isn't placed into our database unless they actually buy something. My problem with that is that we don't have a way to contact them later unless they sign up for the newsletter.

Another problem with the Google Checkout option is that it completely bypasses the checkout page. So if you are using other payment systems the customer doesn't see it unless they missed the big honking google checkout button.

My reasons for wanting to use Google Checkout is simple. We started selling more once we started using gc. I can't say that it's because of GC, only that after the gc merchant logo showed up next to our google base submissions showed up our traffic and sales increased.

Now don't go jumping on the GC bandwagon because I said it increased our sales because to be honest, one or two sales a week isn't that big of a deal. I'm fortunate that I'm also an ebay powerseller so that sales venue pays the bills and keeps me in good standing with Papa Johns Pizza. So if you're doing fine with a different checkout system, don't go changing things because of my sales increase.

Now all I have to figure out is why people aren't buying. I'm getting lots of traffic but not allot of purchases. dadgumit.