Upgrading to a development snapshot I currently use Drupal 7.0.

I am thinking that upgrading to 7.x-dev would resolve some performance issues I have.
Do you think that upgrading a production site to the development snapshot would break any possible database upgrade path?
It is safe to use the 7.x-1.x-dev version now. The updates happen incrementally, based on a number that is updated for every new update function.

It was only before the 7.x-1.x-beta releases, where upgrading was not supported (And apart from some bugs during the beta IIRC) for the -dev version.