1. It depends on the product. For a product with a higher frequency of repairs I consider the warranty as a major part of the purchase.
2. IMO, cables either work or don't work, and generally don't wear out. 90 days on a cable is fine, it gives enough time for someone to tuck it away while other parts come in, then test it once the system is ready. The switchers, converters, and other parts take much more daily wear, so they should be warranted against premature failure. 1 year minimum, but 2+ years demonstrates confidence in the product.
3. No matter what, this will always be controversial. As stated in other replies, good customer service trumps many other problems with a manufacturer/retailer. That said, it's not very fair for the manufacturer to eat the losses that result from this. I feel that it's up to the business to determine which side of the fence they'll fall on. This type of policy is something I maytake a look at when making a purchase, but it wouldn't carry any significant weight in my decision. It would be more of a tie breaker than anything.