I have had my Retrax for 2 years now and love it. However, I would recommend the manual version, not the power version if your planning on doing a fair amount of offroading. You dont want to have a locked cover due to motor failure.
I have a horizontal rack in my bed. 1 spare and two 5 gallon fuel cans and it works pefect with the cover. You just cant use vertical rack and a bed cover together.
That's one of the good things about the roll-n-lock, it's got a manual override in case something goes wrong.