The reason I am skipping shopping cart is not entirely because multiple check out. It's due to my special needs. I am developing an education site that allows people to register for courses, and buy other regular products as well. The shopping cart fits the regular products well.

For the course registration and payment, I found out I need to twist everywhere (screens and processes) to treat a course as a product. Once a course is paid, I still need the registration record. Refund is also tricky. I also need special report.

I am not sure if I making the right decision. Since I am skipping the shopping cart, I think I also have to code my own credit card payment module.