I have used extensively both the POD X3 Live and now the Helix at home, home studio, professional studio's, and lots of live gigs as well.
I actually had very good experiences live with the X3 Live, and great recording experiences. I had lots of good sounding gigs using the X3 Live into tube amps fx loops, and all by itself a few times as well.
The Helix is definitely a significant step up improvement from the X3 Live. Everything is better although I still like LOTS of the legacy effects as well (and they are all present in the Helix in addition to the new models). The amps and cabs are definitely better in Helix and the Dirt boxes are much better. It is much easier to get great live straight to the PA sounds with the Helix providing everything (amps, fx, etc..).
The scribble strips and snapshots are awesome features that make live changes way to easy, you can get super creative here if you want to.
I am very happy with the Helix, but you do certainly have to spend some time dialing in the sounds you want to accomplish (as with all modelers and most any rig as well)
Agreed with the others, buy it from Sweetwater or someone that has a good no questions asked return policy and try it out, you'll have fun.