I just bought the Firehawk Fx and am extremely happy with it. I don't have any of the bluetooth or latency problems some people have mentioned. Of course, I just bought it now and have updated to the latest firmware version so that may be a part of it. I admit it is now selling for $350 so that is one of the reasons I got it. However, I read all of the reviews and watched a lot of youtube videos first. Based on the Helix coming out and past experience on other products with Line 6 (and all the other modelers from Digitech, Boss, etc. - they come out with a new one almost more than once a year) I didn't expect a lot of updates/changes with this unit. I almost got a 500x but I really like to be able to use my iPad or iPhone to edit and store tones and also to be able to use the bluetooth to stream music (don't need another cable hooked up!). I also like the fact that they put the HD amp/effects models on here but also all of the other amp models as well. To me, the Firehawk is really a combination of the Amplifi, the 500x, and the X3 Live. I had an X3 Live and really loved the amp models and sounds out of it. That's why I got it instead of the 500x.
FYI, I just play at home and don't play live, so this was not a consideration of mine. I plug the unit into studio monitors (not too expensive ones) and through headphones and play along with music or guitar instructional videos through my iphone or iMac. Unlike some reviewers, I really like a lot of the factory presets. I find a lot of them I can use to play along to almost any song (may not use exact amp, etc., but sounds good enough to use). I will sometimes adjust gain, bass, mid, treb, etc. but since those controls are right on the unit it is very easy to do. That is another reason I got this versus some other units on the market sold by other companies. I really like having those controls right on the face of the unit.
That was my 2 cents :)