My answers:
1. No
2. If there's a way for me to get more miles, I'm all for it
3. Yes
4. For a big purchase, only if the product/service that the business offering miles provided was about the same as the product/service offered by a competitor. Miles would be a tiebreaker between two comparable products/services, but I wouldn't pick a business whose product/service were otherwise inferior just to get the miles.