haha well, Ive found what Scuzz once said he found, when you run through water, it seems to run straight to the air box opening, and im sure if you have no lid, its going to go right into the filter, also, when i rode with the stock lid, my filters got packed full of mud after like 3 rides. the EHS lid basically fixed all that for me, ive had it for like 3 rides and my filter looks basically new still, and also, if your worried about the 130$ fee, they sell just the kit for $95, thats what i did, you just have to line it up and cut your own hole, and drill the holes for the bolts, it took me like 30 minutes maybe to cut the lid and put it together. worth it to me to se like 40 bucks.
but as for running without a lid, i guess it depends on what you do, i would say no if your in: Mud, water, sand, dirt trails, an race tracks even. if you ride on pavement im sure no lid would do great.