I have one and I find that it does help me, especially with my weakest fingers, the ring and pinky fingers. I use it throughout the day and as part of my warm up and then I'm much more likely to hit and stay on the strings with those last two fingers. If I skip it and don't use the strengthener I rarely land on those strings correctly starting out.

Something else that is also very helpful and will help you strengthen even more is finger dexterity and strengething exericses on the fretboard. Lisa has spider legs warm up lessons found here... https://www.guitartricks.com/lesson.php?input=12293 I know there are more on here too if you search for finger exercises or strengthening/dexterity, etc. There are also many books on "Finger Gyms" you can find,too. (I just got one and it's full of exercises! I always use some to warm up.)

I'm sure others will have some thoughts and recommendations, too.