If you've never tried them, you should
I bought one pair of these for my wife before buying these from backcountry.com as she would get sore and tired after longer ski runs. After the first day, she skied stronger, faster, and didn't complain of the soreness she had felt the day before. I haven't used them for running, only for skiing and it does seem to decrease the lactic acid build up in the leg muscles. You can still get tired but not fatigued like you may without them.
I won't say it makes me 10 years younger but I will say, I don't ever feel like I need to rest because of tired or sore legs.
I also recommend if you're between sizes, go with the smaller as the tighter compression worked better for me.