Shipping fast - how, though?

Shipping fast is important - you get a sense of movement and, more importantly, receive user feedback.

In your experience, what works best:

• ship imperfect features - then circle back and improve them.
• ship improvements to an existing feature until you nail it, then move on to a new one.

Concrete example:

I'm working on a twitter-like fitness app where people post different kinds of updates (meals, cardio/workout sessions, physique updates, etc).

I shipped a good-enough-but-could-be-way-better "post your meal" feature.

Moving forward, I have two choices:
I can either improve this feature or build another good-enough one.

What do you think it's best, and why?