Difference between planning a project vs. planning a product

Question

I have read in numerous places that when developing a product you need to take a different approach to when you are developing a project (think "contract" work).

Some differences are:

1) There is no definitive user, but a "user-base".

2) You need to develop the minimal marketable feature set.

3) Scheduling needs to be watched, as there is not often a fixed deadline it is possible for the product to run overtime (or for scope creep).

I was wondering if there are people out there with experience in both, and if they could offer some input into any differences that they know of. Also if anybody could provide any tips/good references for how to deal with the differences I would be most appreciative.