General What's the benefit of using a launcher over TouchWiz?

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http://androidforums.com – I'm happy with TouchWiz. But I'm out of new things I can make my S3 do. Would a launcher be a worthwhile new toy? What can they do beyond TouchWiz? Should I wait until my AT&T phone gets JB before installing a launcher? I.e., will there be improvements to the TouchWiz UI that I would evaluate first? Is it easy to return to TouchWiz if I don't like the launcher? Thanks! :) (General)