Brother,
I can share shortly my exerience. I have first come to know a group of people through Bible distribution in my locality. We then had some wonderful time together and so I understood that they followed the teachings of Watchman Nee and Witness Lee. At that time there was a conference to be held and so I decided to go (I must confess hastily...).
But I spent some 2 days with them and also took part in one house meeting. There are several things that I admire: they are warm and welcoming, they sing almost constantly.
But on the other hand I had really difficulties accepting some of their practices and doctrines.
1. Yes, they do believe that once you are saved, you will never be lost (or you will have eternal life - no matter what). This is frankly unbiblical and very dangerous!
2. "Calling on the name of the Lord" - I have never understood the verse (2 Timothy 2:22; 1 Peter 1:17) as literally repeating the name of the Lord constantly. I do not believe that the first believers did it either.
3. Preaching : as you mentioned earlier there were books from Witness Lee. I am not generally against Christian books. I have read some books of Watchman Nee and can only recommend them to any believer (The Normal Christian Life, "Sit, Walk, Stand", The Overcoming Life). I truly believe that Watchman Nee was a servant of the Lord. Having said that, I think we should be very careful.
I believe that it is very important that the preacher (or elder) knows himself personally the Lord! Because if he is blind - he cannot lead other blind people (what to say about the seeing) to life or to Christ even if he has all the right theology in a book. (And that applies actually to EVERY CHURCH. So using books for preaching - we should be careful there.
The other thing that disturbs me actually more is the emphasis put on the teachings by W.Lee. And so I fear the people get indoctrinated without really knowing the Lord. ..
Personally, I find it very difficult to read the writings of W. Lee. I have tried several times and I find myself just struggling with so much words.
But I will advise you to be very careful. I can understand that you really enjoy talking with other people after the service, that is generally also good and necessary. We must always beware that the church does not turn just into social gathering! Wherever you go to church, your Number ONE PRIORITY is and should be to WORSHIP GOD! And God Himself must be pleased!
Pray and pray, continue to pray! Being a part of godly church is very important!
As for me, I still keep contact with some of them, but I do not worship with them. It will be difficult for me to do so, for the reasons above mentioned.
May the Lord lead you into His gates!