#1. Not enough room - My 2nd biggest issue - cars and locomotive are twice as long a HO.
#2. Too expensive - This is probably my biggest issue.
#3. Not realistic enough - Other then the third rail, manufactures have a lot more scale equipment now compared to back in the 70/80.
#4. Reliability problems - I have/had more problems in HO (and DCC) then with any O gauge I have had over the years.
#5. Lack of technical knowledge/ability - Learn as you go. But the same issue as other scales and/or Hobbies.