We use pipe-flo to model our flare system and it works okay. We do have a fair numbe of program problems but to be fair, we have set up the model in a very complicated way that makes the solutions much more difficult than they could be (but that is the way the group responsible for the flare system wanted it. Though they don't try to run the model, that's my job <g>).
The advantage of Pipe-flo for us is that we can enter a wide number of different molecules to simulate the various streams in the refinery.
For your industry, are you just interested in modeling liquid systems and what are the types of streams? We have another model that I can't remember the name right now that is used to model the fire water system. The person who uses that one says it is much easier to construct and solve a model than Pipe-flo. A lot of the decision will depend on what you are modeling and how complex your model is and what you need it to 'produce'.