I am also a long time and big fan of amazon.com; wherever possible i order from them.
Their shipping (especially prime) is extremely fast, and their return policy is excellent.
I do think josh is going too far in talking about the savings of free shipping when ordering heavy items; when you order something from an online-only store, and they are willing to give you free shipping on a very heavy item, you can bet that heavy items are already priced to include most of the shipping costs. The only sensible way to compare the savings when using amazon prime (which is like $79 a year) is to look at how much you would pay if you ordered through amazon, but without Prime.
Amazon Prime is, however, great for impatient people since you do get free upgrades to 2 day delivery and cheaper overnight delivery].
FWIW, I ordered from ROADRUNNERsports via Amazon, the item price was less than other googled sources, it weighed 32 oz., and shipping to Hawaii was via Priority Mail and free. I think all items from them ship free. Perhaps this instance will help other sports fans. I have no ties to Amazon or ROADRUNNERsports.