What did I do before Synchronous Modeling? For starters, I would spend hours hacking and slashing models to get surfaces to match up without any witness lines. Also, with many hours of converting and remodeling suppler parts from other 3D CAD systems, let’s just say… it was a major factor for my aerodynamic head.
But, before I jump into my view of synchronous modeling, I think it’s worthwhile to mention the three technologies that form the basis for the geometry component of synchronous modeling:
With “change” technology, you have to modify the face in some manner. Either by move face, offset region, resize face, and make coplanar. With this command the technology moves the selected face and adapts adjoining faces to accommodate the change
The “delete” technology is employed to remove faces from a model. This technology is the foundation of the delete face and cut face commands. The delete technology deletes selected faces and heals neighboring faces to close the open area left where faces are deleted. Delete has enhanced support for merged faces and dependent blends.
The “re-blend” technology is a companion to “change.” It is employed to adapt blend faces when selected faces change (move and offset), and also applies to constant radius rolling-ball blends.
Now with all that said. Wouldn’t it have been nice to have had that technology in older versions of NX and UG…..  Yes, I said it…. UG! In those days the boss would be breathing down my neck, waiting for a part and even a drawing, to be pushed out for a supplier or manufacturer.  Don’t get me wrong, I would have been on the side that would have said synchronous technology was GARBAGE!  Thankfully, that ridiculous stance about the technology is long gone today, much like my knuckle dragging, mouth breathing, Darth Vader of a boss. So any opportunity to work with synchronous modeling, and I’m on board to use it and would say give it a whirl. It will save you time and hopefully your hairline.
Also if I may suggest….try  Xform! It’s in the edit section and is the greatest feature in my single page book.