Yay! definitely yay!

We had ours from about 4 or 5 months. He didn't like it for long periods of time in the early days, but as soon as he could sit up by himself he just loved it. We used it as his highchair when he was first learning to eat solids (we did BLS) and it was great because when he tipped food over the edge it didn't splat everywhere because he wasn't high off the ground.

As for putting them up high on things, we did, but only because DS was not a wriggler, and only ever when we were there with him. We used to sit him on the kitchen bench while we cooked dinner, and it really gave him a different perspective. He would always look forward to cooking time. But if you have a wriggler this would be just too too dangerous. Although he still fits in to it now, we rarely use it anymore - except in emergencies. So he has to be content watching the cooking from his high chair which isn't quite as effective.

As for using it as a portable high chair, I don't think it is the answer. They don't pack down and can be quite awkward to carry when you are carrying everything else including a baby. If your bubs can sit up by themselves you are better off getting something like the Phil & Ted's Me Too chair which clips on to the side of the table. It folds down completely flat for travelling.