I re-targeted some of the bugs that were "obviously" the same SpecConstr issue to 7.8.4. There are a few others that should probably also be re-targeted, but I couldn't tell from a quick scan of the long comment threads.

Looking at the 7.8.4 status page, it's now quite clear that the SpecConstr bug is a show stopper i.e. it affects lots of people/core libraries and doesn't really have a good workaround, as turning of SpecConstr will most likely make e.g. vector too slow.

On Tue, Oct 7, 2014 at 11:23 AM, Johan Tibell <johan.tibell@gmail.com> wrote:
On Tue, Oct 7, 2014 at 10:12 AM, Simon Peyton Jones <simonpj@microsoft.com> wrote:
| 8960 looks rather serious and potentially makes all of 7.8 a no-go
| for some users.

I think this is the big issue. If you look at all the related bugs linked from #8960, lots of users are affected. I think this bug alone probably warrants a release. We should also move all those related bugs to the 7.8.4 milestone, so the impact of this issue is more clear.
 
My conclusion

 * I think we (collectively!) should make a serious attempt to fix show-stopping
   bugs on a major release branch.  (I agree that upgrading to the next major
   release often simply brings in a new wave of bugs because of GHC's
   rapid development culture.)

 * We can only possibly do this if
   a) we can distinguish "show-stopping" from "nice to have"
   b) we get some help (thank you John Lato for implicitly offering)

All sounds good to me. I can help with backporting bug fixes if needed. In return I would encourage people to not mix bug fixes with "I rewrote the compiler" commits. :)

I would define a "show-stopping" bug as one that simply prevents you from using the release altogether, or imposes a very large cost at the user end.

Agreed.

-- Johan