the marketplace says 'yes'. they are popular.
long term resale value says 'yes'.
Swiss build quality is no myth, reliability, performance.
i've owned darTZeel amplification for 10 years. my NHB-108 stereo amp I owned for 7 years. i sold it for more than i paid for it originally after that 7 years and still to this day it is competitive with the very best. i've owned my NHB-458 mono blocks now for 3 years and they are amazing.
I consider the darTZeel to combine the best of tubes in terms of naturalness and a rich transparent mid range along with the speed, low noise, leading edge snap, linearity of solid state. they sound like music.