I have to assume they'll have a "Migrating To Compose MongoDB" article in a few months...

I'm not sure if they do but how much does Compose actually contribute to the project? Will they contribute in the future?

Are they simply a parasite or will they invest in their business by improving the software they sell? If they won't then I would never use them for anything as they are providing a service for a product they have no control over and no desire to invest in and improve and I'm not interested in tying my business to that.