Actually, Charlie, damping factor can be a major issue on longer speaker runs or with speaker cable of inadequate gauge. With a very reactive speaker design, a low damping factor in the amp can lead to really crappy sound.

As a general rule, a higher damping factor means that an amplifier has relatively low output impedence. The flipside is that this is usually accomplished by using a substantial amount of negative feedback. Lots of negative feedback can lead to an amp design with phase shift and distortion problems.

A very simplistic explanation of damping factor is here:

http://www.crownaudio.com/pdf/amps/damping_factor.pdf

Cheers,