This was exactly what I was looking for, and I'm surprised it hadn't been invented long before now!
I've had mine for a few weeks and here are my observations:
Pros:
- brilliant for indoor storage
- actually looks weirdly cool when on
- fits my medium mtb perfectly
- dries quickly
- comes with a handy carry case
Cons:
- bit difficult to put on sometimes - though you will rapidly get the hang of it
Summary:
For those living in apartments or who don't want to scuff the walls (my landlord was getting nervous about the newly painted hallway, hence the purchase!), this is a perfect solution - you cover the messy bits but still have access to the frame so you can carry it around. As mentioned, it is a bit difficult to put on at first, but practice makes perfect; I can get mine on and off in less than 5 minutes. Well worth it.
They're really well made and I wouldn't hesitate to buy additional ones should I buy more bikes!