[Sorry all about my previous email, I accidentally clicked "Send" before typing anything.]
I don't personally get value from the HP, but my understanding is that universities do. In particular, I've heard stories of professors teaching Haskell courses and being able to ask their admin staff to "Install the Haskell Platform" on the lab machines and then they tailor the course materials to content in the HP.
If the HP were to go away, I feel strongly that we should have a deprecation phase. Otherwise the users who do use it will feel like the rug was pulled out from under them. Let's not cause that sort of pain if we have the power to avoid it.
I agree with Gershom that having a minimal installer is the right way to get going for professionals and hackers. I'm less in tune with beginners these days, but I think Gershom is basically right when he says the are a very diverse group and there isn't just one profile that fits the majority of them.
On a personal side, I'm not sure what is entailed in giving objective info about stack vs. cabal. I'm probably OK with it for some definitions, but if it means giving stack equal status, then I feel that is a bit premature at this point. In particular, cabal has the advantage of being established, mature, and battle hardened. Stack, in my opinion, still needs time to prove itself. Both have flaws, both have advantages, but only cabal has a track record at the moment. Yes, I'm being conservative here, but I think that's reasonable if we're talking about making recommendations to such a wide audience.