I'm using FMJ Injexions with Helix single bevel broadheads. I'm using them for the penetration properties.
The only issue (and it's a big one) is the relatively lack of choices for broadheads and worse, field points of the same weight with the Deep Six threads.
Regarding tuning. I shot these arrows through 5-6 of my bows. They were more finicky than either my MFX Classics that I used to use and the Axis Trads I used last year. For some of my bows they were easy to get "bullet holes" (I paper tune, eyeball, and then check with broadheads).
However, I wanted to shoot these arrows (460 spine) out of a specific bow (Bob Lee Ultimate - 47# @26"). It took a lot of tinkering to finally get that one tuned. It would have been easy if I was willing to shoot arrows that were 3 inches longer than my draw length but I don't like to do that. I ended up adding more weight and cutting the arrows 2 inches longer than my draw length (an inch longer than I prefer).
Ironicaly, after two months I decided, on a whim to try a different bow (Habu Mamisha-1 piece -- 49# @26") and it tuned perfectly right off the bat.
I can't comment on penetration in a deer yet. I've gone longer this year (at zero) without a shot than I've gone the last 4! I can say the Injexions shot in a homogenous foam that they penetrate a couple of inches further than the Axis Trads.