Woah! That LED thing is cool! I have a Light Boy and I gotta say... it doesn't do a whole lot.
I thought it was amazing when I was a kid, though.
Why did I stick with the Pocket? One reason is that I will never modify my original Game Boy. I want it to stay the way it's always been for purely emotional reasons. Another issue is that I don't like the way the SP feels. The biggest one, though, is that I have issues with backlit screens; if there isn't an option to crank them down to a super-dim setting, playing is uncomfortable. I seem to remember the SP being very bright and lacking adjustments, but it's honestly been so long since I touched the thing that I'm not entirely sure that's true.
If my DS Phat or DS Lite could play original GB games, my Pocket would probably go into hibernation. I love those systems. They feel great, sound great, and their lighting is fantastic for me. The Phat's glow is modest and the Lite has several settings in between that and supernova.
I don't know why I don't have this brightness problem with television screens, though. I enjoy my Game Boy Player a lot, but I do prefer to retain the personal feeling of playing a handheld when nobody's around to be an audience.