I am a service coordinator for this brand. What type of bi-parting door are you looking for? I would assume a Sliding French by the phrase - rolls smoothly, but we also have the lift and slide. If you can be a little specific as to his concerns I will try and address them for you.

amber windows- Thanks for offering to help. DH is worried that the smooth operation we saw in the showroom will not last and we will end up with a difficult to open door as the only access to the back yard from inside the house.

These are the type of doors I'm talking about:

Thanks for any input you can give.

I personally have sold many of this type unit if these are the standard slider which they appear to be. The only thing you need to do is clean the track out regularly as crap tends to collect which will bind up the rollers. If you go with a lift and slide style the track becomes a much lower profile and this becomes less of an issue although the then the door panels tend to become somewhat heavy and the handle for the lift action can require some strength

It's an OXXO USFD that you are looking at. Millworkman is correct that the debris in the track is the key element in causing the door to operate roughly. Installation is also key. A plumb, level, and square door will operate like a dream. The Lift and Slide is meant for a new construction application and has a 7/32" tolerance on the sill. Not much can collect there, but you are also not rated for water infiltration. 9 pounds per square foot is the approx. weight on the panels. It all depends on what you are going for in regards to design.