It says it is not very good. There are a lot of problems with Cloudsearch. By contrast, Elasticsearch is great and not too difficult to run yourself in AWS, or indeed elsewhere.

Aside from product differences, Cloudsearch was phenomenally expensive, particularly if you had a larger dataset but low read/write volume, as Cloudsearch did not use EBS (at least not in a way you could control), unlike RDS for example.

Nothing? Amazon has lots of Amazon + non Amazon services. They know people use Elastic Search, so people will give them money. Therefore make it.