I just put one together.
Got a couple of 6 cell Mag Num Star bulbs from Pacific Instrument, one of the parts suppliers listed on the Maglite website, along with some switch caps and o-rings I needed for some nearly ancient D cell Mag lites that were around the house. New 2C light from Home Depot, a foot of 5/8" inside diameter heater hose from the local auto parts store, and the last of a box of Surefire CR123 cells. From what I read here, frosting the bulb sounded promising, so I picked up a small bottle of Armour-Etch from Hobby Lobby.
The bulbs arrived today, and I quickly put it together. Yowza! Beam was all full of the usual Maglite artifacts, but seriously bright.
I took the bulb back out and tried out the etching goop. My technique was to get some warm water running in the sink, then smear a generous coat of the etching cream on the bulb with a q-tip. I kept smearing it around for 15 seconds, then rinsed thoroughly. When the bulb is still wet from the rinse, it looks like nothing happened, but when it's dry, the bulb's appearance changes to a nice hazy surface. The difference in the beam is remarkable. The bright hot spot remains in the center, but it's smooth, as is the spill. Very LED like.
Maximum bang for the buck, from what I've seen so far.