Two tips:

1) I use this as a rule of thumb; only launch when it feels like it's version 3.0, not version 1.0. This keeps you on your toes and provides a much better product from the beginning. Remember first impressions are everything, and if customers come and see a smal set of features, they most likely won't come back.

2) Never ever change prices. Unless you're making the product cheaper. If I were to sign up for a service that increased its prices, I would just try and find alternatives. As a customer, it feels like I'm being cheated. Instead, label it as an early bird offer. 30% off in the first 3 months kind of thing. Comes off a lot better.