Usability group

About month ago I visited usability lection and there are key points.
1. UX professionals show UI prototypes to users before ANY programming. Obviously, everybody else should do the same.
2. Paper is better for prototyping than any software (including Balsamiq Mockups).
3. Very small changes in visual design can make big difference in profit. The only way to find out how to change the design is experimenting with real users.
4. There was a link to http://uxmatters.com – I find it interesting.