Diving into piping modeling, finally, and I'm starting to hate the "Cannot connect parts" error. It seems like Plant3d doesn't care to give you any hints about /what/ could be wrong, or allude to what caused the error - just a simple "NOPE." "CAN'T DO THAT." and a cold shoulder.
Currently trying to trouble shoot creating custom parts as the catalog has no expansion joints that I saw. They basically look like "Inline Valve, Sphere" but it's not a valve, so I didn't want to use an aesthetically similar but functionally different element.
///ETA - ok, well, solved that problem. 
/ETA///Very frustrating at times, but overall it's been good. I had high hopes for the structural modeling aspect of it, but it's unrefined to the point of being unusable. Online statements seem to indicate that the structural modeling is not actually a core feature of Plant 3D but rather there for simple augmentation, rather than for structural modeling, detailing, etc. That's very disappointing if you ask me, as it was a selling point to some of the decision makers, from the reseller and much of the Autodesk media. I don't know how you can call a software package a "Plant design" application if you can't even do walkways, stairs, or crossovers accurately. I'm relegated to doing them the old fashioned 3d way in regular Autocad, and xref'ing them into Plant3D - or if I have a 2d-only drafter do the structurals, I'll use Plant3d to whip up quick mass-elements to get a good layout indication, until the other drafter can finish his drawings and I can model something from his plans (not ideal, but necessary sometimes)
Piping and equipment has been reasonably impressive so far, however, though the learning curve is a challenge for custom parts.
