The user interface to set up your model, it's easy enough for someone who has not used this program before but also allows you to use advanced features if needed! It can be difficult at times when running simulations of large models (i'm talking about simulating an entire city). If there are multiple people working together in one project then communication between them becomes very important as they each need their own version/copy that will work with everyone else involved - so I have found myself having more than 1 copy open just because we all want our individual versions without sharing others files or overwriting other users' changes etc., which makes things quite messy sometimes! Also using different file formats such as.dae vs dxf could cause some problems trying get everything synced correctly again after saving new updates from another person; however these issues do become less common now due to upgrades being made regularly by eCosimm Pro team members themselves making any errors much.