We have the G4 powerset, my wife can use hers without any issue's, so I disagree that it's hard to use, and she still struggles with our tv/blue-ray/surround sound/etc remote that we've had for over a year. Maybe on day 1 it takes some getting use to, but not after you figure out what button does what function...
I really like the built in FM tuner on the G4, I use it every day when commuting to work.
And the helmet speaker volume does not seem weak at all, I don't even turn mine all the way up and it sounds great.
I've never used the Sena, so I can't comment on that, but I will say the G4 does
not suck, slick unit IMO!