Actually I take it back about it not showing a proceed to checkout link on this site. That is what it shows as soon as you add a download product to your cart if you are not signed into the site, and then clicking it will prompt you to sign in or register and then after you sign in it will show the paypal button.
Whereas if you are already signed in then you will never see the proceed to checkout link unless you are using authorize.net., instead it will just show the paypal and/or google checkout buttons.
So if you are not signed into this site and you add a buy joe a beer to your cart it will immediately show the paypal button and it will not show a proceed to checkout, but as soon as you add a download product to the cart then if you are not signed in it will hide the paypal button and it will show the proceed to checkout link, again clicking that link is just going to prompt you to sign in or register.
If you have a download product in the cart, once you sign in it will show the paypal and or google checkout buttons.
So people can buy me a beer without signing in but they have to be signed in to buy a download product.
Hope that helps,
Joe