800,900 and 1000 series heads are pretty much bullet proof.  The 900s came out with aluminum gear boxes to save weight and they had problems with them so IH updated most of them back to cast iron as I understand it.  Our 963 still has aluminum gear boxes and other than adding a little oil at the beginning of each season we haven't touched them in 11 years.  The weakest part of those heads is probably the idler sprocket for the gathering chains but it's the same sprocket that Deere used and they are cheap so just plan on replacing them every year or two depending on how many acres you cover. 

A neighbor went from a 1063 to a 2200 and wished they would have kept their 1063, they then traded for a Drago and got and loved it at first but after a couple of years they didn't feel it was anymore reliable than the 1063.  I like how the Drago and Gerringhoff head are built heavy but if parts last twice as long as on our 963 head and cost 3x as much I don't see that you are gaining anything.

If I was going to change something about our 963 head I think they should have lowered the auger trough 3" so it would carry more corn without throwing it out of the trough but when those heads were designed they weren't thinking about pushing 2,000 bushel an hour through a 6 row head so that wasn't an issue.  I'd like to try cupped flighting on our cross auger and then convert it to hydraulic drive off the reel drive so we could vary the auger speed as needed.