db,
I'm not expert, but typically when you use KVM switches or A/B switches, you are introducing longer cable lengths and typically more places for the video signal to get weaker. You really won't notice it unless you use extremely high resolutions such as 1600x1200 and do lot of desktop publishing since it seems that your fonts appear slighly fuzzier than normal and not as sharp. For normal usage, its unnoticeable.