I live on a hill in a large city and do not drive, so hitherto taking my DB out has been fraught with issues. The Double Bass Buggie - as recommended by my DB teacher - makes it easy to manoeuvre my instrument along typical city pavements, on and off buses and such, and to gigs / jam sessions / lessons / rehearsals etc.
It's easy to take on and off once you know how, but mine came with absolutely no documentation whatsoever and I had to first look up the manufacturer's website for instructions. Turns out that it's not quite as easy to steer the buggie-enabled instrument as I'd hoped, and I've found it this does sometimes (not always) veer constantly to one side when in use. That said, it's a great deal easier to transport the instrument than it was before I got the buggie, and it's also possible - not having had it that long - that I am not consistently attaching the thing correctly. The documentation makes no mention of this issue; presumably, DB players are expected to work out for themselves how to ensure stable steering.
Life is much better than before, no doubt; there is also room for improvement in the documentation and consistent steering stability of the product. Hence four, not five stars.