For users of MaximDL, here is a really cool plugin (free). Its called multiguide and allows you to select more than one guide star to guide on - simultaneously!
It takes the average error of multiple stars providing greater accuracy than a single star. I've used it twice with good results. Noticed less correction being made, but nothing quantitative. Will need to give it more time.
Anyway, its here if you want to try it (obviously you need MaximDL first
)
http://winfij.homeip.net/maximdl/multiguide.html