I have had three rolling covers:
1). Armor-roll - don't even think about it
2). Roll-n-lock - three major issues: i). Vinyl gets white lines on it when driving with cover open due to rubbing against aluminum slats, doesn't come off ii). Freezes shut easily in the winter. iii). Strap to open and close can get caught in driveshaft while towing
3). Retrax - best of the three IMHO but I did have some damage to my rails due to a problem with the latch, need to see what manufacturer does about it. Locks open all positions, low maintenance, does not freeze shut as easily.
Hope that helps.