The HT hotend is a great upgrade if you have a flexion extruder and are no longer printing flexibles. I bought a Flexion Extruder a while back, intending to print some of Flexion's ultra-low durometer TPE. I've since switched back to mostly printing PLA and PLA+, mostly without issue.
If you're familiar with the Flexion Extruder, you may recall their comparison chart. Diabase has since changed their chart (it now predicts excellent print performance for PLA with the standard flexion extruder), so I'm not sure if their current extruder has been modified. In any case, their chart originally showed that you may experience "mixed results depending on brand / quality of filament" and that it "may require extensive fine tune adjustment". Micro Swiss's current chart reflects this. My experience with the standard flexion hotend seems to reflect this as well.
I've been trying out a variety of filament colors and brands depending on current projects and I've noticed that some brands take no calibration, while I can spend hours trying to dial in others. Swapping out to the HT hotend has significantly cut down the amount of troubleshooting required when I switch filaments.
It's not noted in the description, but the "thermal tube" appears to be a capricorn tube rather than the white PTFE pictured.
If you have a custom heater block mount, be aware that the base of the barrel (where the flats are cut out) is approximately .5mm larger in diameter than the original flexion barrel.