I hear that a new version of stable has been released, which was based on testing, and ever since then new packages for my testing install have been becoming fewer and farther between. Shouldn't it be the opposite? If they were planning on freezing testing so it could be come testing, once stable came out shouldn't testing be getting a load of new packages from unstable? Does it think I have stable installed now? Do I need to do something? Or have there just been no package updates in the past few days?

If you have your repository set as "sarge", then you followed sarge from testing to stable. If you have your repository set as "testing" then you would not follow sarge, you'd now be using etch. After making sure your repository is set however you want it and running apt-get update, you may want to try a apt-get dist-upgrade which will allow any more radical changes to be updated.