Looks just as useless as every other SLA I've seen. Even the longest outages only get you a 25% refund, with no compensation for incidental damages. Furthermore any outage due to force majeure or "the actions of you or any third party" is excluded, which can easily be construed to mean just about anything.
And the refund is... in S3 credits!
They can be down for 7.3 hours in one month, and all you get is a 25% discount?
They would have done better to say nothing.
It's worse than that. They can be down for 7.29 hours in one month and all you get is a 10% discount. You get 25% if they're down for >= 7.3 hours.
The gist of it is a 99.9% uptime guarantee.
For certain definitions of the word "guarantee"
awesome, S3 is one step closer to being a true CDN.
We're Committed to One "Nine" of Reliability! (tm)