This case holds a TomTom wide screen sat nav, but you have to remove the mounting attachment and there is no room in the case for cabling etc - it just holds the sat nav itself (but this is all it is advertised to do, so I'm not complaining). I have bought one of these and I also have a bigger case that holds the sat nav with mounting kit plus cables etc. This one is more useful if I park somewhere and I have to carry the sat nav around, as it is small enough to fit easily into a bag, and I leave the cables etc in the car (out of sight of course). The larger case has the advantage of being able to keep everything tidy in one place, for instance if you are taking the unit indoors and you don't have to carry it around.
This is made of a fairly tough plastic, although it is flexible and wouldn't protect the unit from a serious impact or being dropped a long way. But as I would only really use this to store the sat nav inside a larger bag or rucksack this isn't really an issue. Again, I would use my other, larger case if more protection was needed.
So, I would recommend this case, but I believe it complements a bigger case rather than being an alternative.