I do not have doubts about the doctrine. - no serious doubts, at least.
For example:
- the year when Jerusalim was destroyed issue - some say according to history it should be a few years before of after - to tell you the truth I do not care if that profecy points to 1914, 1913 or 1915. (And am not saying I do not believe in 1914, I just did not dig deep into these calculations and into this research and I will not, because I am fed up with numbers - I am an accountant :) ). So no matter the year it started, it is very clear that Satan and his angels were thrown on the earth. I do not need to know the exact year and month.
- about the changes in the doctrine: the changes themselves show they admitt they do not know everything, and that they are imperfect humans. every time they change something they say it loud and clear.
I do not think we should expect from this organisation to be perfect, or from the governing body. It is afterall an organization made by imperfect humans, and they say it too, that the organization is not perfect, and nor them are perfect. It's not like anointed ones know Jehova's mind. Jehova reveals what he wants when he wants. He is perfect. But we are all, including the anointed ones and the GB, we are all imperfect human beings trying to guess what will come, what's the meaning of past events and hoping to survive ...
The "doubts" that I have are related to certain mindsets some JW's have:
For example, I think most JW's have this mindset that we should allow ourselves to be happy only in Paradise. Most chose things that would just assure their survival in this world, what is good for them (good like in mediocre, not like in really good), or what they imagine God wants them to do, but not what would make them really really happy. For example when they chose a job - they chose what is practical, not what they love ... or some start pioneering but are not made for this, and makes them unhappy ... this goes up to choosing with whom to get married, for some ...
I belive we should get rid of this idea that we shall be happy only in Paradise. I believe that God wants us to be happy here and now, too. And we can be happy here and now, respecting God's principles. And God Himself wants this, too. He is afterall the happy God.
And I am not sure that this mindset that some have is promoted in the publications. I think it is more an interpretation or a missunderstanding of some JW's. Especialy lately, I feel something has changed in the publications, like they promote more individuality and personal decision, and they point more towards the essence - love, kindness etc.
It is curious how people imediately notice change related to doctrine, but they do not notice change in mindset and in the advice about life that is given in the publications.
About the field ministry - It is the duty of the GB and the annointed ones to urge us all about the field ministry - as some publications admitt, this ministry was given to them, we are just helping them out. And my personal duty is to try to make myself happy. So I go in the field ministry as much as it makes me happy, and as much as I am joyfull about. I used to pioneer and I realised it was not for me and I was not happy during all of that time. (for some time of my pioneeing I was - in the beginning I guess). I also tried not going for a few months and I honestly missed it. So now I am doing as much as it makes me feel happy and joyfull about what I do. And it does feel good to tell people about this hope we have, I can not imagine life without knowing what I know about the purpose of God, about the reason why evil exists and bad things happen. Of course you want to tell others when you know these things. And what other religion teaches this?
As I said before, I know the organisation is not perfect, but it is the closest to the first century christianity as it is described in the Bible. What more do you want in an imperfect world? We will see a perfect organisation in the new world.
PS: Sorry for the possible spelling mistakes - my first language is not English, as you might have guessed ...