I liked the design when this set released, though in hindsight maybe it was just the rainbow backs reminding me of my beloved 89 Donruss. Bonus points for the full-colour backs (Topps hadn't yet figured out how to do that) and multiple *different* player images! I've got to dock marks for including only one line of stats and for the microscopic biographical info, though that's how they made room for those images.
The fronts were okay -- clean and simple like 1990 Leaf. Perhaps the wear-prone card stock and sloppy quality (typos, duplicate/omitted card numbers) were what relegated 91 Ultra to the junk bins.