As much as an issue the reticule bloom seems to be for most people I have a far bigger gripe with the jump heigh and movement speed for Spartans.
Powerhouse, as an example, contains so many ledges, jumps and other geometry that break that flow of movement due to the reduced jumping height. Ledges and jumps that years of Halo playing have taught me to be able to jump simply get in my way and defy my basic expectations.
Jumping around seemed to be an integral part of the Halo sandbox and in Reach it feels sidelined, hampered needlessly. In past Halo games I could recount the seemingly endless amount of times a well timed or lucky jump saved me from danger from rockets, grenades, vehicles or who knows what else. That seems to be missing entirely from Reach. Not saying it is, but it just seems that way.
How many times have I jumped over a Ghost boosting towards me in Reach? None. How many times have I jumped just outside of the blast radius of a grenade? Once, maybe twice. Escaped from a surprise rocket attack? Never. How many times have I failed to make the jump onto the ledge in the middle circle of Powerhouse? Too many damm times.
It's the sole reason why I prefer Elites in Reach, they have the jumping and speed that I'm familiar with. When playing as an Elite, I don't miscalculate jumps. The game plays closer to my expectations as a Halo player. You even go as far to say that the regenerating health of the Elites also plays to the strengths and preferences of the average Halo player.
I do have issues, some, with the bloom/reticule/whatever, but they pale in comparison to the fundamental issue I have with simply controlling my Spartan. It's goes against expectations and, ultimately, it's simply not to fun to play as Spartan.
The role of the Elites in multiplayer really needs to be expanded - I hope they do get their own playlist. Otherwise Custom games will be the only alternative for me to play the game the way I want to play it.