Blizzard has just released several videos from the 'World Wide Invitational' where SC2 was first announced. They've also released a whole bunch of audio clips for several units. From what I had seen on the blizzard forums prior to this was that not many people were very happy with the current unit sounds. It looks like they are trying to get a good idea of what people like and dislike. It's great to see that the development team has been putting at least some effort into paying attention to what the community likes and dislikes. Hopefully this will add to the overall quality of the game.

Here is the link to the videos:
http://www.starcraft2.com/movies.xml#wwi

The audio can be found on the pages for each unit.

Also, for anyone who doesn't follow the blizzard forums I've added a few more posts from blizzard employees including one from the lead game developer in the articles post.