I am using Clever Cloud for months (since January) and I am quite happy with it. I am in fact using it as a simple Couchbase service provider but also to host some of my apps. (Note that Clever Cloud does not use EC2 but have their own servers/infrastructure)
I know another service that offer Couchbase as a Service: http://www.kurobase.com/ but I have not yet tested this one.
Oh, I didn’t catch CleverCloud was not on EC2. I will try KuroBase!
Also, I attended your presentation in Seoul last week. Thank you for the great presentation too