Well I went through the same dilemma. I had no choice but to pull the trigger on a 2015 but all things being equal I would have preferred waiting. That said, I am pulling 35-40K combined with the 2015 and it pulls very well. The other thing is, at least here, a lot of guys are trading year to year for only a couple K. The resale on Duramax trucks is really strong. So if you decide you want the 2017, I don't think it is quite as expensive to upgrade as you might think.
As to potential first year issues, I bought an 01 GMC 3500 D/A. I had to replace the computer in 100K. I bought the extended warranty with it because it was first year powertrain. The extended warranty paid for the computer and it was dollar for dollar the same as I paid for the extended warranty.
There certainly could be some issues with the new powertrain, but I personally would be willing to risk the $65K on the fact that there wont be much to be concerned about. There is the extended warranty you can buy if you want the extra insurance. I will be looking at purchasing a 5500 in 2017 if I like what IH and GM put together. If I don't like the medium duty trucks, I will pick up another 3500 that hopefully will have the tow ratings that Ram and Ford have.