I'm familiar with the open G thing, because that's how a dobro is tuned. I use that when I'm goofing off with a slide, and also what I call D tuning. I've written some really cool stuff dropping both, or sometimes just the big E string to D.
I use this quite a bit when I'm performing too, lot of country stuff these days where this is used. I can catch some ear twisting bends too, pulling down on the 5th, 4th, and 3rd string. Even have banjo tuners on one tele, just set the stops, and then just turn the key when I want to drop. Sometimes I drop it to C also, but can do more dropping to D.
It's alright to experiment with alternate tunings, but make sure you spend just as much time using standard tuning. You can try the half step down if you want, but if you've gotten used to the way your guitar sounds, you may not like it. I can tune my guitars by ear, and be within two cents of standard. Therefore tuning each string down a half step, to me makes the guitar sound out of tune. This trick is sometimes used for a vocalist to hit a note they can't quite reach in standard tuning. I know of several genres where this has been used, and I've had to transpose some songs recorded this way. It's next to impossible to do this without an electronic tuner, and it is harder to play with others that aren't tuned this way.
In all the years I've played guitar, I think I've done that twice. I sat in with a band once that tuned everything a half a step lower, and the other time I was just goofing off with a new tuner. The choice is yours to make on whether to try it, and I'm sure there are other tunings that I haven't even tried yet.
JD
