A brief review of the
A brief review of the literature doesn't seem to support a significant physiologic performance advantage, meaning that any measurable performance improvement could be due to placebo effect. Mention has been made of lactate recovery in the South African study but not having seen the study methodology myself, I can't endorse that effect as being statistically significant since I don't know the values, the sample size, how well matched the participants were, etc. Unfortunately, no one's thought of a way to blind the study (making it so the participants don't know if they're wearing them or not the way drug trials use real and placebo pills) since anyone can tell if their socks feel compressive or not. For this reason psychological effects (placebo effect) can't be factored out.
More agreement exists that they aid recovery by decreasing post-exercise soreness, although since there's no consistent physiology to back that up either, the reduced soreness could be partly or entirely psychological as well.
However, I have never heard of any way that they could be harmful, so if they make you feel better (which is really what counts), wear them!