Tested on acoustic and electric guitars
Positives:
You can adjust the pressure it exerts on the strings
It folds and becomes quite small compared to others
Overall, it is satisfactory in its use up to about the 7th fret.
Although not mentioned, it also works for electric guitar.

Negatives:
You need to adjust the pressure almost every time you change frets, if not every 1, every 2 frets to have an ideal fit, which can be tiring if you have many changes.
After the 7th fret, the metal is very likely not to be enough to cover the entire fret properly. As you go up, the frets lengthen and at some point the low E string will either be in the air or buzz. Of course, it is relatively rare to use it so high, but know that you probably won't be able to use the thick E string.
It is better to choose another one for serious work...