What is your definition of a well-designed product? Example/Why?

A well designed product is one which seamlessly performs as the customer thinks it should, and expects it to, and is easy to use.

An example is a product which gets fewer support calls.

Another definition is a product that is reliable, and doesn't cause systems or the OS to fail in the worse case, or leaks memory. On the web you don't want to over burden the client or make too many trips to the server.

A well designed product is one that in a way you don't notice, because nothing bugs you. A poorly designed product, for example is one that you can't even authenticate (in otherwords you can't use your userid and password to get into or there are severe complications.)

For an example of a good platform design; within the .Net framework, code is compiled rather than interpreted as ASP script is; this aids in early binding of objects directly resulting in performance gains. Since state management is handled within .Net, lines of code can be eliminated and this reduces the time required to load functionality.

Less processing time between pages contributes to an improved end user experience. A cleaner code set makes upfront development costs per feature less expensive, Web applications quicker to test and deploy, and as a bonus are easier to maintain and update.

I think a great product should be fun to use.