When I first started, they were the impetus for me to begin transition, because for the first time they showed me that even someone as masculine as me, and in my late 20s, could still get hormone results good enough to look more or less completely female. Once I knew that, there was no stopping me.
In early transition, they were still an inspiration, because as I was getting depressed about my lack of progress, I could look at them and say "okay, here's where they were at ___ months on hormones, and they're not much more feminine than I am now. Chill. It will come.
In late transition, they did nothing but trigger me because I was lagging WAY behind schedule, and it seemed like every single one of them ended up looking completely naturally-female to my eyes, while I was stuck feeling very mannish and unpretty.
Now, I don't watch them at all anymore. No need. I get all the validation I need in my daily life now. At best I use them to inspire others, at worst they're still making me depressed because I'm jealous of how beautiful others turned out.