I used that or something very similar to that (the one I used was called "FasterPing" and was in beta, that could be it but renamed, they do the same thing) while playing WoW for at least two years, when I was playing competitive or semi-competitive PvP arena and battlegrounds, and in WoW for me it did have an impact, both on the listed ping times and on the "feel" of lower latency. I also never had any instability at all.
I was also playing Aces High during that time, but I never found it to make a difference for Aces High. Even for WoW, I would recommended it to people I was teamed with, and of those who installed it, only about half said their ping numbers went down, the rest claimed there was no difference. So it was hit and miss.
One down side is that I seemed to notice slower speeds for other tasks on the internet, such as downloading files. I'm not an expert on TCP-IP, but it seems to make sense that Microsoft would tweak the default connection settings for the most common user tasks, which probably is not playing MMOs, but probably is transferring files and web browsing.
I'm not using it now since I'm not playing WoW any more, so I never reinstalled it after my last OS reinstall. I'd say that it probably won't hurt to try it, but not to get your hopes up.
