I use the Boss NS-2 pedal. It really cleans up your sound a lot. When I play at volumes from 0-6 (on my AVT50 Head and 412 cab), my telecaster is silent and so is my Duncan Distortion-loaded Ibanez. However at stage volumes (10+), it will still feedback if you don't keep your hand over the strings. What I'm saying is that even though it feeds back, it is controllable, and that's the main thing.
Only downside I've seen is that when I use my Boss RV-3 reverb at the same time, the NS-2 cuts some of the reverb out. Not a big problem, since when I use the reverb I'm playing clean 90% of the time. Other than that, the NS-2 seems to be pretty transparent to me.
Out of all the pedals I've ever bought, it is the best investment I've made (the NS-2 and the powered Pedalboard being the two most important investments I've made.) It may seem like a lot of money for a pedal that doesn't make a noticable difference in sound (such as modulation pedals) but I never think about playing loud without mine... literally.