Here are a couple of experiences I have had in regards to hall assignments:
1. After I graduated from high school, a few classes that I needed to take in college were on my normal meeting nights of Tuesday and Thursday. I switched halls to one that had Monday and Wednesday evening meetings. I never got any "flak" from the elders for doing that. This hall was also nearly 20 miles from where I lived.
2. While living in another state, I attended a congregation roughly 30 miles away so that I could be in the same hall as a good friend of mine. There were approximately 10 other congos in the area in which I lived, but I never once attended any one of them on a regular basis. Again, no guidance or suggestions from the elders asking me to attend my "assigned" hall.
3. Right now, we live outside of the territory of the hall we go to. The PO's exact words to us and others who asked us about our living outside of the area was, "It is the decision of the head of the household as to what congregation they would like to attend." The PO himself lives outside of the hall's territory too but was asked by the CO to stay after a reorg that happened over a year and a half ago between two congos.
I guess I am not the one to ask about problems with hall assignments. I know it happens and I know of people who have been chastised by the elders about it, but personally, I have never had a problem.