They look a great product, but I would have two main concerns, as I do a lot of decorating I work on the stairs a lot, which is quite different from just going up and down them. concerns would be:
1) That the rods could be a trip hazard themselves - as you walk down the stairs and the back of you heel catches the bar and rolls your foot forward making you unbalanced.
2) What sort of tension is the bar under? more oftern then not a dust sheet is folded in half then laid up the stairs, so it becomes extra slippy. If the dust sheet starts to slip, is the bar under enough tension it stop the slip or would it pull the bar out?
I'm not trying to pick holes in the product, just like to find out a bit more and seeing as you've used them, you have some idea of how they perform. I'd like to know how strong that spring is. The price of these is great so you can't grumble but my gut feeling is i'd pay an extra £10 if I could get these with twist lock