I have an EOTECH 552, a 512, and an ACOG 4x with the piggyback Docter red dot. All of my optics have throw levers for quick change.
When first deciding on optics, I went round and round about EOTECH v. Aimpoint. Aimpoint's only advantage seems to be long battery life.
I finally decided on EOTECH after speaking with my nephews, who at the time were both active-duty SEALs with sandbox experience. (Pretty cool, huh? Two guys in the same family who are SEALs. Hooah!

). They said that the guys in the Teams liked the EOTECH, and that was good enough for me.
I bought the ACOG with Docter red dot before going to Thunder Ranch for Defensive Carbine. Used the EOTECH for the entire time. (Only one target was past 100 yards/meters). I have the dedicated 552 on the 5.56mm upper and the 512 on the CMMG .22LR upper.
One cool thing Clint taught me about the EOTECH during CQB training in the Terminator: if you place the red dot of the EOTECH reticule even with the top of the head of the silhouette, the round will go center mass of the target's head.
I like the ACOG, but it doesn't get used much, as almost all of my carbine use/training is less than 100 yards. (Note: Loc n load's post above is consistent with my own experience). The piggyback red dot on the ACOG is overkill; the Bindon aiming concept works well enough, I think, and for really close stuff (bad breath to two arms' length distance) point and shoot per Rob Pincus and forget the sights.
In closing, optics are fun and useful, but iron sights still do fine work. I would buy a dedicated .22LR upper or good rimfire conversion unit before I bought my first optic.
