I think it would be a pain for people playing ME2 first and then going back to ME1. The whole Mako thing, the framerate and pop-in issues, the inventory management, the lack of interrupt system, smaller normandy, smaller crew, less "active" conversations (in ME2 they actually walk around or move more etc.), all of that might let them feel disappointed, whereas playing it in the order it's supposed to be played, will make them enjoy both more, because the first one is a fresh experience, and they'll understand the story of the 2nd one better, and they will feel the improvements instead of a downgrade..
Truth does not fear investigation