I was gentle parented in the 70s due to my mum being very interested in attachment and no-smacking parenting theories, and it was different than 99% of my peers.
In general, I think it's a very good approach and much better than most, if done properly. Very close to my mum and talk to her all the time.
The negatives- I was scared of adult disapproval my whole life, my mum did that raise an eyebrow thing and it just terrified me, scared of teachers as well, even though nothing ever happened to me. Might have just been me! Also parents usually want their kids to do what they want, and so the raised eyebrow is just another way to achieve that. I have felt a bit dependent on my mum, even as an adult as the supportive/gentle approach continued into adulthood. I feel that less now.
One other thing, coping with the behaviour of many much more irrational, difficult, shouty, aggressive people has been hard, it's taken me a long time to toughen up and also see people who are more manipulative, that's been quite an important life skill I perhaps didn't get from a more nurturing approach, I assumed everyone was nice like my parents!
It's still a good approach, in the early years, I was probably a tiny bit harsher and more shouty with my own children, which I regret at times (as it was a function of my stress). It's better than constant overt control over children which is hard to survive.