Good Question.
I suppose in my case it has to come in 2 parts,
Firstly when I was a believer, I was grateful for understanding the bible as I never known it before, I was raised a catholic, I learnt scriptures and How to use the bible, I now know how to use it as well as Priest, Pastor Clergyman etc… and that’s including handing many other translations not just the NWT.
Because of all the reading I was doing, I am a much better reader, because of the Door to Door work I can just walk up to someone anywhere and anytime and talk with more confidence. I gave talks which helped me not only in Pubic Speaking but also how to research topics.
Secondly, as a NON Believer, I am now grateful because once you have being fooled by the best you know how to handle the rest. I can see though these other mind-controlling religions and I can see these mind-controlling methods used in other areas other then religions as well. I am a greater believer in God and Jesus then ever before but I can see the lies in all religions, and I can see that simple keeping the Law of Christ is really all that matters, details about understanding every single scripture isn’t really that important.
I am not as bitter as many other Ex-JW’s because I am not DFed nor did I ever DA myself either, why let the WTS have their satisfaction, I’ll beat them at there own game.
I also gave up a good job so I could go pioneering for 10 years but it’s the cost of false religions, look how many in the history of mankind have suffered and died for false religion, the Inquisitions, the crusaders and even the Muslims now, we are just more victims.