It's a very hard topic to discuss calmly on any xJW board, but I think it is worth it.
I for one have kept a lot of good memories of my JW time, especially of very nice people I dearly loved.
In a more general way, I would agree with Wildhorses' comment about racism. And I would extend it to the JWs' stance on nationalism and war. Even though I don't (and deeply didn't) agree with the motives for such a stance, I must admit that it kept me in the organisation in spite of my doubts for some time. Another nice thing was to live in a community of people in which you could practically trust anybody. I know there are many counterexamples but I just didn't happen to be personally disappointed in personal relationships.
Now does that outweigh the horrors of the system (mind control, blood policy, dfing, shunning, etc.)? Certainly not. But I think the positive has to be acknowledged all the same. At the very least with a view to communication efficiency: when you tell people who do have some positive experience in their belief system and community that everything in it is wrong and rotten, they just cannot believe you.