being a avid airsofter, i might be able to give a little insight.
Airsoft, to me is about goin out and playing "guns". we all played it as children, i still play it. its a way for me to get out and run around too, somthing i seem to have less and less time to do.
i hate to compair airsoft and paintball, as i think its a totally different animal. but in both we run around and shoot eachother.
Airsoft is all about "Milsim" we strive for realism(well as much as you can get with a toy gun that shoots 6mm bbs)
FPS rules where i play are 400 FPS for AEGs(automatic electric guns) 600FPS for sniper rifles(gas, electric or spring) most GBB(Gas Blow Back, IE the slide/bolt cycles with each shot) pistols are around 250-300 fps. Most properly upgraded AEGs can reach out to about 200-250 ft accurately.
sniper rifles i have seen around 350-400ft.
As for pain when hit, its depends on where your hit. if your hit in your gear, your wont really feel it, but hear it. hits are all honor-based. you know your hit, you call it and take the "death". easy to cheat, but oddly enough most players dont, and if they do, track your rounds into their face.(its a courtesy that no headshots are taken unless you can hit a helmet or other headgear, if they wear a facemask, they are asking for a head shot.)
i have been playing airsoft for almost 7 years now. At the present time i have more in airsoft than i do in real guns(dollar figures).
i currently own(airsoft):
Socom16
10.5 AR
m249(my money pit, currently at $1500 and about 60 bux a game to use)
fullsize USP
sig 226
I have owned:
ak47
m16a1
glock 18
USP compact
g36k
remmington 1100 AOW
m9
wilson CQB(fullsize)
p90
mp5
TMP
A couple M203s
all of my "guns" are metal where is needs to be(IE everything thats metal on the real thing is metal on their airsoft counterparts.
I own 17 different camo BDUs with roughly 14 different types of rigs, ranging from BHI ISSAK, to a paraclete RAV, my next purchase will be a wasatch in MC(and possibly a CIRAS)
i play every month(for the most part).
Most ppl would say im nuts, or stupid for spending that much on "toys" over real firearms.
all i have to say to them is, in the last 5 years i have purchased 19 real firearms, and im back down to 4, one of which is in a different state. (got layed off, hard times hit me, boohoo.) i only regret selling my benelli M1, which i just replaced with an m3.
i can go play airsoft for 60-100 a day, whereas when i go shooting it runs me 200-400 a day(i have been known to pass 1000 rounds in a day when i go shooting.) so cost is an issue.
(sorry about the last part, but i know im gonna catch hell for having all this invested in airsoft.)