Many have cut their springs, but most of the stock 4th gen coil springs should not be cut(they are not the correct type that can be cut safely). Some people do it anyway, but I highly recommend against it.
The only type of coil spring that can be cut safely is tangential(the other types are square and pigtail). The rear springs on 4th gens are pigtail on bottom and square on top, so can not be cut safely. The exception to that is if the springs are progressive with tightly wound coils near the top(I know for a fact the rear RT springs are like this....not sure about other models). Technically you shouldn't cut the progressive(tightly wound near the top) square end springs either, but after cutting them the coils are wound so tight they are nearly square ended again. Once you put very light weight on them(barely start to set the truck's weight down) they flatten out and sit in the spring perch safely.
I bought a set of RT springs for my quad cab and cut them as much as I could(I ran out of tightly wound progressive coil) and I got nearly 1" of rear drop. Also, even if I had more coil to safely cut, I couldn't have because the spring was becoming too short to fit. There is nothing that holds it in place other than the vehicle's weight, and if I cut the spring any shorter I'd be afraid of it falling out if I hit a big bump or something that fully extends the axle.
Check out this website, a lot of good info here:
Also, NEVER cut with a torch, and NEVER heat springs to let them fall/sag and cool. Doing either of these is a huge safety concern.