Let me preface this by saying I literally did nothing more to my Kemper than turn it on, plug my Guthrie Govan signature model guitar in, and plug in my Bose QC15 headphones. Believe me, I know Bose headphones aren't the best way to judge the Kemper.
That said, my Yamaha DXR10 won't be here until the end of the week and I couldn't stand just letting my brand new Kemper just sit there without hearing what it can do. So I plugged in as above.
I went through LITERALLY every profile that comes standard on the Kemper. It had some decent clean tones. But there was not a SINGLE distorted tone that I would use. If I had to play a gig with the way this thing sounded through headphones, I'd cancel the gig rather than play because I'd be too embarrassed to use these tones.
Every high gain tone, sounded like the old Boss Metal Zone pedal, just at different volumes or different gain settings. Some of the profile names are almost insulting to the artists they're supposed to "replicate". For example, there were a couple on there that had some version of Eddie Van Halen reference in the name. The last one I tried, sounded more like Pantera's tone than a Van Halen tone.
I'm still going to give this thing a fair try when I receive the Yamaha DXR10. And maybe tomorrow night (since I don't have my Yamaha yet), I'll hook it up through the power section of my Mesa Roadster and see what it sounds like through that using my Mesa cabs. I'm positive that will sound better than headphones. But the whole point of buying this was to NOT have to lug around the amp and cabs and to use FRFR so I can hear exactly what the audience hears. But if this is what it's going to sound like at a gig, I'll be lucky if there is a single "audient" left. LOL
I probably shouldn't have even used the headphones. Because after what I heard tonight, it's only increased my skepticism.
Edit: Full disclosure, after plugging this into the Yamaha DXR10, I fully admit that this unit sounds WAAAAAAY better than through the Bose headphones!