I'm really interested to hear more responses to this as it's something I've been thinking about for a while. After I started getting my own acrylics done (badly) at 16 then training myself, I feel that can be a lot of negative stigma on using e-files. For me, I have to confess in previous years I've used the fact that I hand file only as a selling point to my services, as the majority of people in my area have suffered from NSS salons so, like me, link NSS with e-files.
The more I now research e-files and courses, and the more I see techs I respect using them I wonder if, when I'm more confident with my application, I'll do an e-file course myself. I struggle slightly with filing as I have slight early onset osteoporosis in one wrist from a break so I find my other hand compensates and I'm locking my fingers when filing, which has led to filing too roughly and sore hands!