We have an IVT and really like it, over 6000 hours. Somewhere near the 2000 hour mark we had a problem with a hydraulic pump. Other than that it's just worked. Whatever reputation you think the IVT has, I don't think there have been a lot of problems in recent years across all the units sold in total. There are always the odd machines with lots of problems, but I don't believe it's general. John Deere has two different IVTs. In the smaller tractors I think they use a transmission from ZF. The 7 and 8 series are made by John Deere if I remember correctly. We're not doing any draft pulling. This tractor has spent it's life pulling a sprayer (lots of hydraulic flow under tough conditions to drive the sprayer's water pump), mowing, pulling wagons, loader work, and auger work. We would never buy a replacement machine for these purposes without IVT or a CVT. Especially for spraying. We have always used HyGard II oil in it. Not sure if that makes it work better or not.
Fendt's CVT is the oldest, most efficient, and most proven CVT in the industry. All other CVTs and IVTs are essentially copies of it, with various changes to get around the patents Fendt had and has. It's also extremely simple, mechanically. Far simpler than a powershift transmission. Unlike other brands I don't think they have to shift between a high and low range to get the full speed range. With fancy computer programming the other companies have managed to make their CVTs and IVT almost as smooth and seamless as Fendt.