I got one, but I've only used it a handful of times. Most places don't have a problem with me bringing in the folded bike, and at the places that do, the cover probably wouldn't help. I don't regret getting it, but it's a "could be useful," not a "must have." It's not the first thing I would get if my budget was tight.

ETA:
Has anyone figured out a cleaver way to use it as a saddle bag with taillight? If I hand it from the back of the saddle, it covers where my seatpost taillight goes. I need a taillight a lot more than I need the cover.