genim, I’m with you; a plugin like this should have far fewer problems than it has, and users shouldn’t need to be constantly implementing hacks in various bits of code.
If you need to be a developer to get it working should you do anything slightly out of the ordinary (like use Google Checkout instead of PayPal!) then Instinct should say so.
Sorry for venting, but I’ve been trying to find out how to get Google Checkout to work for weeks now with no joy (although a few suggestions for code hacks that don’t work). I’ve wasted a lot of time, $100, and potentially damaged my credibility with a new client by choosing this product.
If I can’t get it working soon I’ll have to write off the time and money.