Ask YC: How to launch?

We are going to launch a bug tracking tool shortly. The product isn't completely ready but some of the core features are usable. We want to do a limited release so that the product can benefit from some customer interaction before we promote it aggressively.

Do you think that a invites-only beta is a good idea for such a product? Is there some other way of doing a selective/limited release without over exposing the product before its ready?