I saw my first one in 'real life' (as opposed to in a photo) at Beaulieu on Sunday, looks good and I like the fact it's removable. The alternative is tinting but I'm not sure I like the look.
This is definitely now on my 'Car stuff to buy' list!
My Cayman R came with one fitted - I ended up removing it as I found is obscured visibility too much when on track. I still sometimes put it back in when it's bright, and take it out for track days.
Yes it just clips into place although I’ve never taken it off. I guess it does restrict visibility but no more than having darkened glass but it does stop people looking in the boot.