I know someone who broke an IE shaft. IE denied the warranty.
IE input shaft broke by a 400hp truck with single disc TC and stock flex plate. Shipped it to OPIE and he told me it was cooked wrong and he would cover it. So two days later it's over 2yrs old no warranty!! Bad thing is it was a bad shaft to start with so if your looking to buy a IE shaft you better put your power to it before the 2yrs.
I think the big boys are going with the Sonnax 1 pc.