experience is the product
The product is just a small part in the entire experience. Here's a great set of slides about creating the experience:
It's almost impossible to know the user's context. Ergo, build, measure, unbuild. Repeat. Of course, learn from other people's measurements.
Creating Passionate Users is another fantastic resource about creating the experience. It is an entire paradigm shift on how to think while designing a product.
Which brings me to Tufte - on the reading list for next weekend. His focus is specifically at data rather than a product, but it is eventually all the same. Will write about it later.
[Update: I later read this post and realised that the ideas I mention here seem disconnected: end-to-end experience, learning and gathering feedback from data, user-focus, and presenting data. Apologies - I was thinking two steps ahead of what I was writing. They are all connected and in a later post I will tie together the connections.]