I haven't found a way to do this as a batch process, but removing them from the catalogue and re-importing them won't necessarily work. I'm still using LR 2.6 as my main Lightroom editor, but I've also been playing with LR 3. Because of the meta data associated with each file, when I import a file I've worked on in LR 2 into LR 3, it automatically comes in with the develop features already applied. The only way to get a 'blank slate' so to speak would be to create a new folder, copy the images to that folder and then re-import them from there. I tried that for a while, but it was essentially doubling the amount of drive space used. And yes, a batch feature would be nice!
Mike.