To be more specific, there's two things that I'd like to check out:
1. The pricing.
2. Ease of use - for me, that is: the presence of the REST-api.
Currently, my projects make use of MongoDB from MongoLab.
I'm building using Unity3d, so I'm using the REST-api to make sure that it'll work
building to all platforms. (MongoLabs REST-api is identical to that of Parse,
which I was using before: https://parseplatform.github.io/docs/rest/guide/)
I hope gearhost will offer better price/performance than Mongolab and also supports
access to the database using REST-api.
If that's the case, gearhost would be my future choice for MongoDB hosting.