Similar to TANNER I've dumped most of my optics and sights and just gone with iron sights.
You can use precisely-zeroed optics if you want, but wind, random chaotic variations in hopup, shooting while moving, etc, are going to limit how well sights work.
To be good at outdoor airsoft, you need to take shots, evaluate those shots, and follow up with more shots. Once you get reasonably good at this method those follow up shots will usually be out of your barrel before the first ones have fully passed your target, since you'll know early on whether they'll hit or not.
Also to add to someone's post above... Some people who do not appear to be using their sights are in fact using them. I'm one of those people. I often vary the amount of alignment of vision through the sights depending on how much precision I think I actually need, weighed against how quickly I need to make the shot. A casual observer might see me drawing a sightline two inches above my sights and conclude that I don't use my sights, but I'm still using them -- it's just that I'm so used to them that I can work out a rough sightline 2 inches above the sights without having to get a perfect cheek weld.
On the other hand, in many situations (especially when sneaking up on an enemy guarding a target), I'll look directly through them if I can and be as precise as I can.
Both methods work well for different situations, but the bottom line is, you need to spend a huge amount of time aiming and getting to know your sight picture and the characteristics of your gun really well..
Lastly I'll mention that I've tried out a couple heavily-magnified ACOGs here and there and while I personally don't use them ever, I think they are pretty damned useful for reconnaissance as well as evaluating shots and planning followup shots. With magnification, you can track a BB for much longer than without. That said, the extra weight, the terrible eye-relief through goggles, the overall usability, the glare, the cost and the poor close-to-midrange performance has steered me away from these otherwise cool devices.
Iron sights for me.
Now you know