Receptacle on floor?

Does it make any difference if receptacle is place on a concrete floor with hardwood or on concrete wall or gypsum wall? Your opinion is appreciated.
I have both types of outlets (in wall and in floor) and I notice absolutely no difference. I think the key is to use good quality outlets. One good example is the Porter-port as seen here on Audiogon. There are several others available at different price ranges
The above poster is right... the ONLY caveat left is to use a hard cover for floor receptacles, brass, steel, etc. as they are exposed to more weighty items than wall outlets would be.

No other diffs should be apparent aside from placement.
TQ for the responses. By the way I m using the Porter Port
I would think that the floor mounted receptacle would result in a "slower" sound from your system. Think about it, all those electrons have to go uphill in order to get to your equipment...