I really like the Nik products that I have (Color Efex Pro 4, Silver Efex 2, HDR Efex 2 and Viveza 2) but never went with their sharpener for some reason. I too, ended up with Topaz (the newest version, 3.1, was just released), have found it to be a great tool and for the money, a great value.
I do capture and output sharpening in LR4, but with my work flow being what it is now, almost all creative sharpening goes through Topaz. It's certainly worth the demo.
Phil