The new Nexus 7 is a sweet device, but it's not uncommon for a new product to have a few bugs. Such is the case with the NN7, which was exhibiting odd touchscreen behavior for some users. Google has confirmed that an Android 4.3 update with a fix for the touchscreen bug is going out now. Indeed, build number JSS15Q is starting to hit devices right now.
Some users in the Google products forum are reporting that the update does alleviate their touchscreen woes.