Hello!
The other day I received a brand new KeyLab 61 MKII, and it is a great controller, but aftertouch sensitivity is not OK to my opinion. It is quite jumpy - goes very abruptly from zero to max both audible and in the recorded MIDI messages. Also, applying the three different velocity curves from MIDI Control Center doesn't make any effect on AT sensitivity. Finally, white keys seem more sensitive than black keys - the same was noticeable in Hydrasynth, but they fixed it with firmware update and different curves for white and black keys. Here I made a comparison between KeyLab 61 MKII, KeyStep, NI Komplete Kontrol S88 MKII and Behringer Deepmind 12 keyboard. What you see are the aftertouch messages recorded by Cubase for each of them. It is clearly visible that KeyLab's AT is very jumpy and not smooth - too few intermediate steps, the curve looks almost like a pulse. On the other end is Deepmind's AT which seems quite smooth and close to sine wave. Komplete Kontrol is second best, and even KeyStep is better than KeyLab, although not perfect. You can see also that exponential and logarithmic curves don't make any change in KeyLab. Do I have a defective unit, or all KeyLabs behave this way? I would say that the AT is almost unusable.
P.S. Latest firmware on both KeyLab and KeyStep. The example MIDI messages are recorded with USB MIDI, Windows 10, Cubase 12