I've been working with the free trial version and I've come to my decision about it.
The good part is Topaz Sharpen does a really nice job. There's a wee bit of a learning curve that has to be gotten over to maximize its potential, but it's a rather gentle one in my opinion and the results, overall, are excellent.
The flip-side of that coin is that Topaz Sharpen runs dog slow on my Windows PC. If I had to guess my GPU, with only 2GB of memory, is just not up to the task as the list of supported hardware on the Topaz website certainly suggests. More importantly to me, Topaz Sharpen isn't doing a significantly better job than what I can accomplish with the standard "arsenal" that comes with Photoshop. Between Adobe's Anti Shake Filter (which does a great job of when the shutter speed used was a little too slow) the counter-intuitively-named Unsharp Mask, Smart Sharpen (which has improved significantly in recent releases) and the High Pass Filter, I feel I have everything I need and really, because I'm familiar with the existing tools, it's simply faster for me to continue using them. I'd be willing to add Topaz Sharpen to my established 'flow if I felt the juice was worth the squeeze but for me... It's just not. For those who haven't sold their soul to Adobe I can see it being an excellent option.