My modified opinion of "the rush" (long overdue)
To be honest, I was among the anti-rush or nerf-the-rush crowd back before the devs decided to implement spawned bosses. My opinions at that time were based on some different conditions in the game, conditions that have changed, and I find it necessary to state now, for the record, how my opinion has changed over time.
The first different condition was public portals. You see, before the nerf the only games you could join were hosted, and every single one of them was a rush. If you need to unlock the levels, you had no chance. People simply played one level over and over, rushing the bosses and saturating the market with pinks. If you were not a bear, you would get booted from these games.
I still feel it is uncool to rush in a public instance. I feel it is downright evil for a high level player to enter a public instance and run ahead of the low level players to kill the boss and leave.
But I feel strongly that, given that there are now public instances, a private instance is the maker's personal space (within the limits of the TOS) and any rushing, or skipping of mini-bosses, or other corridors, or to only clear mobs and leave the boss, is the right of the maker of that instance.
The second change is the re-spawning maps. If you are level 4 in FH IV, you can't possibly clear it because they re-spawn too fast. So, in a case like that I don't bother including the first room on the right. In fact, it makes more sense to lead a death train into the treasure room and kite them until they are all dead, then coax Meathead into there for another round of kiting. That's, in fact, the only way a level 4 can survive there.
So that's it. In a nutshell, I have come to feel that it's OK to rush, within the constraints of the nerf, when you are in your own instance or when you are in a re-spawning map. But it's still not sporting to rush in a public instance, and it's bad sportsmanship to rush ahead and kill the boss when all the noobs are trying to clear the mobs.