Here's my quick and dirty answer. A ghille is great if you are willing and prepared to fully commit to the role of sniper/recon. If not, you will be better off not running one because you will get hot and tired quickly, on top of the fact you probably won't notice any advantage while wearing the ghille for the fact that you are not in the right mindset.
Now here's what I mean. The sniper role in airsoft and milsim is not about racking up kills at long range. To be effective you are mostly gathering information on objectives, enemy positions and movement. Firefights are not your goal but rather to be avoided at all costs. Sure sometimes you may get a chance to take a shot at that commander or leader but those are few far and between in airsoft and any distance you gained with the sniper fps rules are easily lost within 20-30meters. So if you aren't willing to perform the bread and butter of a recon element, then a ghille is generally not suited for most people. They wouldn't find it useful for what they are trying to accomplish anyways. Sniper/recon is just a different mind set.
Now with all that said, if you just want to look the part then that's cool too. You just may find yourself taking it off later in the day.
I agree and disagree.
I don't know how it is here in Arizona, I'm from California and we're able to use a ghillie effectively and correctly, we can sit and pick players off, here maybe not so much.
Now, as Sarge said snipers in any set, airsoft, milsim, and actual in a combat situation in which I've been.
There is a large recon aspect, that's why a good portion of our Army's Snipers were once Cavalry Scouts, as I was. We are trained for reconnaissance, that's what the 19D does. 80% of the time, it's just covering other soldiers, which I assume the main aspect here would be, just as it was in Iraq. We performed more missions to keep insurgents off the MSR, or to keep soldiers alive, not to pick insurgents off. From what I hear, the sims out here, there really is no recon to be gathered unless there were games further north, or on BLM land where there are a lot more terrain features and foliage. Most of the people it seams out here (and I very well could be wrong) are the teenage 1st shooter style of fighter.
Another aspect I agree on and Mad Sarge is completely correct. If you're not in the right mind set, if you cannot lay in 15lbs of additional material and vegetation in triple digit heat. Stay away. In order for a Ghillie suit to be affective, there's minimal movement and when you do (I've taken 3 hours to move 100 yards to get one shot) It's snail paced. He's right, you don't run, you stalk. You run (and I used to run 4-6 miles every morning for 5 years) And I won't run more than 200' in a ghillie suit.
If you have doubts just don't do it, if you can't sit in one spot without moving for hours. . . Please don't do it, or you'll get a .36 fired at you.