Fasteddie complains about it, and I'm one of the "ones" that say "Don't do it". The reasons the Manufacturer did it are almost too numerous to list, But Mitsubishi DID pioneer this technology, and several others havs Purchased the rights to use the design from them, including Porsche. They don't rob any power, they last forever, and they work very well. Almost every Manufacturer uses them in at least one engine design, and they cost money to design, and put in. When a Car manufacturer will spend money to put them, when there main focus is profit, they MUST see the need/reason for them. We could go into all the detail that you want, but just do a search on balance shafts (google/Yahoo) and do some reading, and then form your own opinion.
I leave them in, and when I looked for the 4.3 that is in my rig right now, I looked for the "balance shaft version", as one of my requirements.
Kary