One of the things we'd like with AppHarbor is to endorse best practices. This means that you'll probably not be able to run your Azure application in AppHarbor without modifications. This is not due to special requirements for AppHarbor, but because Azure requires special code. On the other hand, you are able to create a template ASP.NET MVC application and push it directly.
Another thing is that we will never provide the full range of Microsoft solutions. Microsoft already does that. Our edge is that we can offer more than just Microsoft products, and as we're running in EC2, there's a whole range of providers offering additional value as well.
For instance, we're going to support memcached, because it's industry standard. Microsoft will support Velocity, because that's what they make. I think this is a substantial and important difference.
To sum it up, we're going to support file storage, message queues and what you need to build a scalable web application. Some may be the Microsoft flavor, and other may not.
Hmm, being on EC2, are you going to provide access to SimpleDB, S3, SQS, and SNS? Seems to me that would bring it pretty close to Azure's feature list.
Another thing is that we will never provide the full range of Microsoft solutions. Microsoft already does that. Our edge is that we can offer more than just Microsoft products, and as we're running in EC2, there's a whole range of providers offering additional value as well. For instance, we're going to support memcached, because it's industry standard. Microsoft will support Velocity, because that's what they make. I think this is a substantial and important difference.
To sum it up, we're going to support file storage, message queues and what you need to build a scalable web application. Some may be the Microsoft flavor, and other may not.