Sanding Roller

[IWalkLikeHimaMartian]

Has anyone used one of these? What is your opinion of them?
The one I am thinking of is the Bosch one, but I am aware that there are others that are cheaper:

 

[Tigercubrider]

I have a lidl or aldi one.

Handy for certain jobs. I was sanding a shiplap conservatory and it was easy to get into the slots

I wouldn't use it for sanding flat wood, as it would be easy to create a dip.

 

[foxhole]

Would think it has very limited use, flap sanders are available for use on drills so pointless extra cost.