What's in a Guarantee

So I placed an order with a company on the 31st of July. At the time, I spoke to them on the phone and they said it should ship in about 5 days. On the 10th I hadn't received it, so I called them. They told me at that point that they were 2 weeks out, but my order should ship "next week."

Feeling neither warm nor fuzzy, I called on the 18th just to make sure things were really on track. They told me it should ship on the 19th. On the 19th they called me at 5am and said it was shipping out on the 20th.

Today I didn't receive it, so I called again. It went out on the 24th.

Another company "guarantees" to ship within 48 hours, but this year they've been shipping in more like 72. They "guarantee" it, but if they don't meet it, there's no discount, credit, or apology. It just didn't happen.

So what's in a guarantee? Or whatever happened to a "gentleman's agreement"? If you've said you'll do something, do you do it? What do you do if you can't keep your word? Should you do anything? or do you just say "oh well"?