We hear you on the cheaper plan; watch this space.
Last, there is no restriction on creating only one database of each size.
Is there some technical reason that you can't offer both?
Presumably, their decision to only support Postgres is partly competition (many others provide MySQL on EC2), and partly technical. How would you justify the technical merits of the decision, without sounding "like a used car salesman"?
Those are the specific features I think that make Postgres a better choice for both use as my day-to-day database and why we chose Postgres over MySQL for building a database service.
Certainly you could build a similar service on top of, say, RDS, but without the features listed above, I think it would take a lot more work and not come out as well.
Hope that helps.
I do agree about them being expensive. Their services in general are too expensive for me -- personally I prefer to manage my own EC2 instances. But they do provide value worth paying for depending on your needs.
I don't use postgres - I hope heroku expands this kind of service to more databases (although I don't think it's likely in the near future).
The smallest database is also pretty expensive. I wouldn't mind a cheaper plan for less resources.
Only being able to create one database of each size is just weird, especially if forking or following. Can anybody confirm that this is a limitation? (I only read about this from one of the other comments here)