With Haswell there were issues like upstream rewriting the modesetting code around the same time (3.6/3.7) HSW was being enabled, and it took a few releases to get the issues fixed (3.8 was still buggy at places).
No the backport had to be done, and to avoid a possible NACK after release it was pushed before the distro kernel freeze.The fact that this had to be back ported to avoid a painful SRU is an organisational issue, not a code issue (would you have bothered with a backport if it weren't necessary to go through the SRU process?) I'm not saying it's necessarily a bad idea, it's obviously a better situation than Debian (where Wheezy is unusable on modern Intel hardware), but it's not ideal.
Yes it's a mess, but getting better with dma_buf and all. The way to get them in sync is to depend on a point-release stack, like for instance the nvidia-prime stuff for 12.04.4 did (IIRC), or at least it was only supported on that stack. Also, it doesn't matter which generation intel you have on a hybrid machine, they should work of fail just the same.Btw Do you think there might be any problems keeping hybrid graphics drivers in sync? Don't the Nvidia drivers get updated often even on LTS? Any hybrid graphics features/changes there will appear in the LTS but without the desponding upstream kernel changes which could be an issue for such tightly linked components. How well does hybrid graphics word with Broadwell and a modern stack anyway, is it still a mess?