Ubercart

Ryan, I'm not saying it doesn't work, I'm saying it is misleading to the customer. The comment you made in point 3 is key -- "even if it's the default option". Let me walk through an example for you.

1. I create a new product, a DVD set (SKU 001). It costs $250.00.
2. The product is also going to be available as a download, but the download only costs $100.00. I add this as a separate attribute / option / SKU. This is SKU 002.
3. The price shown on the product page and in the catalog is the sell price of the base item. Not the price of the attribute, but the base price of the product.
4. I don't want my customers to be scared off by a $250.00 price tag ... by default I want them to see the product only costs $100. It only costs $250 if they want to purchase the DVD.
5. The ONLY way to accomplish this (and to have both shippable and download on the same product page) is to (1) make the base price of the product be $100, and (2) set a price adjustment in the attributes for the DVD to be +150.00.
6. This works perfectly fine, but there is one possible confusion for the customer. When they see the product anywhere in the site (catalog, product pages, etc.), they see "SKU 001" and "$100.00".
7. Now of course, when they purchase the item and go to the checkout, it will say "SKU 002" and "$100.00", but for someone who is looking closely at the products, they may argue that we are advertising the DVDs for $100.00, therefore it should be sold to them at that price.

Does this make sense? It is an important consideration.