I have the Lakeland one, and have bought one for my daughter as well. You do need to have a cover, I find, otherwise it can take a long time for the clothes to dry.
I have the top rail open and just hang the clothes from that and let them dry. If they're not too long, I will fold out the bottom rail too, so that the warmth from that will rise and dry clothes quicker. After a few hours, I go and turn the clothes around.
I didn't like placing the clothes across the rails as I found it left marks across the clothes.
I also find that it can keep the cold edge off a room - it's not going to replace a heater, but definitely raises the temperature a little bit.