I purchased a G50 wireless unit (I have it in my pedal board) and after a couple of weeks, I can say that I think it is awesome. It sounds just like I am plugged into my rig with a cable, and the battery which I have used for 6 hours already seems to have plenty of juice left. I went with the G50 since 1) I have a pedal board already and I use some pedals on there for effects & tuner, 2) I read the G30 transmitter was made of plastic and felt cheap by most reviewers online, and 3) cheaper than the G90 (and in my rig, I would have had to run the output of the G90 back to my pedal board anyway for wah & tuner pedals).
If I didn't need to run the guitar signal at all for my pedal board, I would have gone for the G90. Besides, I think the specs for the G50 & G90 are the same (range, SNR, etc.) so it is not like the G50 is inferior, although the G50/G90 specs are better than the G30.
Good luck with your decision!
Regards,
Juan