What is the most reliable and popular Node.js templating engine?

Node noobie questions I hope someone wise can help answer:

1) What is the most reliable and popular Node.js templating engine? I'm using Express and I'm thinking of either Jade or EJS(Embedded JavaScript).

By the way, is it possible to NOT use a template engine when developing for Node? Or will that cause a lot of pain down the road?

2) Also while we're at the topic of most popular, is MongoDB a wise bet when it comes to database for Node?

Feedback from those with experience in this area will be greatly appreciated.

Thanks very much!

I recommend to use ECT. This is perfomance focused template engine but with very powerful features. It much faster than many others. And have friendly CoffeeScript embedded syntax. You can play with demo here. Also ECT have support for client-side.

I could recommend the EJS, since it allows you to use simple JS in templates seamlessly.
PS Jade is project by TJ, inventor of Express, notable reason isn't it :-)

UPDATE:
MongoDB is very wise deсision, and check out the mongoose module, robust ORM.