I have found it to be very well made and robust. The cross bar on the screw which tightens the clamp is big enough so that you can clamp it pretty firmly and the centre column can be securely fastened over range of heights to cope with hides with the shelf at varying distances below the viewing window. Swapping the centre column between the tripod and the clamp is very easy and quick. I have only come across one hide where I couldn't get the clamp over the shelf and that is the Jordan Hide at Holkam - which has an edging strip attached to the shelf which is too wide for the jaws to fit over. However, somebody has thoughtfully cut notches in this strip, so there are just a few place where the clamp will fit. Frustrating if the hide is full and you can't get a seat in the right spot!
I find I use a hide clamp less often these days. Hide designs have moved on and it is not infrequent to find hides where you can use a telescope or camera standing up with your tripod fully extended. For example the Island Mere Hide at Minsmere or the Parrinder Hide at Titchwell are designed to allow this. Another design I like is the hides at the RSPB's Frampton Marsh reserve where the benches are not fixed down. This allows you to move the seat far enough away from the hide wall so that you can sit behind a partially extended tripod. Nevertheless, many more traditional hides have a fixed bench and a single, narrow window designed for those sitting on the bench. In these cases, the space between the bench and the shelf is too narrow to use a tripod (I really have tried!) and a hide clamp is the solution for me.
The only downside to a hide clamp (apart from remembering to take it) is that any vibration in the hide caused by people moving about and getting up and down is transmitted to your telescope or camera through the building's structure. Of course this happens to some extent however you use your optical gear, but it is exacerbated by having your equipment firmly clamped to the structure. This can get annoying when hides are busy, but I don't usually find it to be more than a momentary issue.