Ask HN: Performance of backend-as-a-service providers?

I'm considering building a SaaS based service for something many developers use within their own infrastructure. Think of things like memcached, redis, etc.

The customer base for this product will likely be similar to those that would use Parse, Stackmob, etc.

How well do these backend-as-a-service providers perform? And where are they hosted to reduce latency for their customers? I'd prefer to stay way from EC2, but it is attractive since it would work well for customers hosted on EC2 or Heroku.

Thanks for any responses!