I've only had very minimal issues with S3... one of the things thats holding me back from switching to a cheaper provider from Amazon is if its not broke, don't fix it.
Individual blob access is not very reliable on S3. In a previous company uploading big-ish (1-10000MB) files was part of the service. We would see failing uploads or slow writes all the time. Make sure to queue and wrap your upload script with retries.
I wasn't saying it was, merely reporting the facts! S3 targets four nines uptime; which is really good but not infallible. For most apps though, I think it's reasonable to accept that if S3 is offline, the app is offline also.
All of AWS has changed significantly in the past 6 years. I think it's disingenuous to say that an outage from that era, for any provider, influences your thinking nowadays.
I'm not sure S3 has changed nearly as much as the rest of AWS, which is probably why it is so stable. Regardless, the point is that outages can happen to S3 as well, and have; just because it hasn't happened for a few years doesn't mean than 99.99% = 100%.