Our MongoHQ integration is very straightforward - MongoHQ provides us with a replica set and we configure it as any other MongoDB database.
Feel free to ask any specific questions.
We showed it to people and we found that one could easily trick the system with things like "Worst American Art Ever". That generates results, but shows the limits of a general semantic search in a narrow context.
Happy to hear any suggestions about how to make something like this both useful and not too easy to make look really silly.
Why do you use both SendGrid and MailChimp for email?
Can you talk about the different use cases that require using the different email services?
SendGrid for one-off emails (ie. a user signs up for an account, their welcome email).
MailChimp for email marketing (we send newsletters via them).
MailChimp has since released Mandrill that caters to the one-off emails, but we were already with SendGrid by then.
Sendgrid is an SMTP relay with high deliverability. That's all it does. You can find who received what on the website, too. With MailChimp you have to setup lists and all that unnecessary stuff.
There's one big drawback to using both: we currently have to sync our users to MailChimp and sync MailChimp unsubscribes back. Hence we're going to get rid of MC eventually when we can build good enough UI to manage mass emails.