I also love my Fender Mustang GTX100 (my initial reviews of it are here and here). I’ve had it since October of last year. Other than the bluetooth music streaming being wonky (I stopped using the BT streaming and just play music/backing tracks through my computer and monitor speakers which sound better anyway, but bluetooth syncing & backup, preset upload/download via wifi is great), I absolutely love this amp! I played both the Fender GTX and Boss Katana in the store (so can’t compare them for long term use), and personally preferred the Fender sound, controls, and features.
While I’ve bought way too many guitars, I stopped looking at amps since I got this one. It’s so versatile and sounds amazing. After messing around with tens of presets for months, I’ve now settled on just two presets that I created using the Fender Deluxe Reverb amp model. One preset for my Strat and another preset for my PRS guitars with humbuckers. Both presets have 5 pedals (overdrive, tubescreamer, EQ, delay & reverb) that I toggle on & off using the footswitch which give me a huge range of tones that satisfy the handful of blues, rock and alt rock songs that I play (I don’t play heavy metal so can’t judge it on that).
For my current level of guitar playing (just under a year), it more than satisfies and exceeds my needs, and I believe it will continue doing so for several years ahead.