ViperGTS:
The G2 still comes with a Lexan lens, it can become brittle however. The aftermarket UCL lens actually allows up to 11% more light through - makes it a little brighter, for 7 bucks shipped, its a nice upgrade.
Fullmetal Chocobo:
The L2 is da' shizzle. I thought about getting one but I like tighter beams better. I'm hoping that for '06 Surefire introduces a new KL4 head (65 lumen) with a tighter beam pattern so I can put that on my E2e - great compact LED light. The L4 currently has a broader beam than I like.
For those of you who have the ol' 2AA Mini-Mag,
this thing makes a fantastic upgrade.
They'll get about 5 or so hours on regular alkalines and a good 7 hours on litiums. Fully regulated so you don't have to worry about blowing it. The clickie switch from that site is nice too. Thier claim of 42 lumes is questionable, but it is pretty bright and definetly blows the stock bulb away.