I’ve been tinkering with Topaz Clarity for a week or so now and my initial impressions are that it’s like the Lightroom Clarity slider on steroids. While Lightroom lets you push one slider, Topaz Clarity lets you fine tune mico, mid-tone and overall contrast with separate sliders. Additionally, you can use a very smart masking brush with edge awareness to fine tune your clarity and saturation selections.
Topaz Clarity Screenshot (Note the edge aware mask view in the top-right corner.)