Hey guys,
I have been following this debate for sometime, and I wanted to let you know how I solved the checkout without account problem. I did not use this mod.
First, i use paypal as my payment processor. I don't take any other payment types. If you do differently, my way won't work for you.
I simply deleted the regular checkout button from my cart. When the customer clicks paypal, they get shipped off to the paypal checkout page, where they will either use their existing account, pay using a credit card without a paypal account (or create a new paypal account, I guess).
When the order is complete, the information automatically gets handed back to zencart and the customer file is created. I have tried to eliminate the whole notion of "accounts" from my site, and for the most part, it works.
The solution is not perfect... and if I do fire up the Google Checkout, I will have to move away from this, but I wanted to offer it up to you as another idea.
Good luck,