I got this to mount my TomTom Rider (originally bought for use with my motorbike) on my cycle handlebars, more out of curiosity, really since most of my cycling is my commute to work along a well-known route. But hey, you never know - I may use it when I'm out and about elsewhere and in any case, the bluetooth facility of the satnav could be handy for phone conversations as I'm puffing up a hill!
In short, the unit fits easily and firmly on my bike; it seems to be water-proof (although this isn't too much of a concern with a satnav designed to be waterproof for use on a motor-bike); and is reasonably visible through the clear plastic window.
The only slight niggle is the need to be absolutely certain that the case has clicked totally into place on the mount before setting off: it has come adrift on one occasion when I was slightly careless about this. No harm done, though because it seems well enough padded (and on this occasion it wasn't driven over by following traffic!)