I've seen the some of the choices made in this thread and I don't really believe Floyd Mayweather, Marvin Hagler, Bernard Hopkins, and Salvador Sanchez quailify as having average hand speed.
The notion that Sal Sanchez had average handspeed is ridiculous. He was quite fast of fist. Chavez, however, had very average handspeed as does Juan Manuel Marquez.
Later in his career, I agree. Earlier, in the mid to late 90s, I thought he actually had rather quick hands, especially with the straight right.