I may be wrong, but from what I've read, the purpose of such products (and I am in no way defending or recommending them) is to reduce fluctuations in the power supply to the DACs in the player caused by EM induction from the static on rotating CDs/DVDs. It has nothing to do with optical data retrieval.
I guess such an effect is possible, but as with cables and other controversial tweaks I'm sure the after-lunch effect (dulled hearing) and psychological effects have more relevance to perceived differences.