I used a pretty good one (Mutec MC-3+USB) into a $6k DAC-Preamp on the Stereophile "A" list. There was a positive difference. Then, I got a newer DAC-preamp ($4k), and I found that the reclocker added harshness to the sound.
My conclusion: this is just as system-specific as power conditioners and maybe even cables. Try to be objective when you evaluate a reclocker in your own system, and don’t buy anything that can’t be returned for full credit. And finally, don’t listen to technical arguments for and against, as many of them are just BS. Listen to the sound with your own ears, in your own system, and if at all possible, make blind comparisons.