I use them for lunging quite often. I think they can be very beneficial, I tend to use them fairly low to get the horse to stretch down into the contact. Not a fan of them being used too high of tightly, though different positions/lengths suit different horses. It all depends on the lunger knowing what they are doing I guess!
I don't and wouldn't use them for lunging, but I have used them (quite loose though) for long reining, when I first long reined my mare to try and keep her straight...
i have used side reins before, and found them really beneficial, when loose and just usign them to aid the work.
hmm unless its a youngster or horse that hasnt been lunged much in the past, i see little point in lunging a horse without some aid, other than to get energy out.