I'm probably just adding to the choir, but here's my 2 cents.
I agree that preordering blindly, as some game publishers want you to, is bad. Really, it's just irresponsible. You shouldn't buy an house without first seeing it in person, ever.
But in this case, it's not blind buying at all. We've got Dev Diaries, we've got Q&A session with the devs, and we've got multiple hours of actual gameplay footage in the streams. There's plenty of material to decide if you are interested enough to get the game as soon as it's out.
So in practice, preordering Stellaris at this point is comparable to when, after a thorough visit to your prospective future house and its neighborhood, you have decided that yes, it's a great place, and you want to seal the deal as soon as possible, even if it'll be another month before you can actually move there. I don't see much wrong with it, assuming you know and trust the sellers, and are fairly confident that they won't mess up the building during that month.
And if those sellers offer some (more or less)cool swag in exchange for moving the money a little earlier than strictly necessary? Even better! As long as the swag isn't the only reason you do it, of course
