Of all the things that you can put to the cloud, I'm not sure why people would want a cloud-hosted memory store. It's easy as heck to set it up in your own server, probably costs less to maintain and host, and faster too as it's closer to your data centers.
If you're using other AWS services, then this makes a lot of sense. It saves you the hassle of setting multiple redis nodes on EC2 and the (admittedly low) maintenance.
They handle automatic failover, which redis does not currently do out of the box. That part is pretty cool. Maybe not worth the price, but definitely useful.
