For me the connectivity of Android based systems is important. I
like to connect with FLARM, variometer and logger. (I am also
dreaming of GPS-NAV communication with XCSoar).
After using Android device going back to Windows CE is not easy.
Mobile communication sends my position into web server, and
maybe I can track my friends online while flying.
User interface is IMHO the problem of all these touch devices.
Simple buttons or rotary switch would be better in turbulence.

For me the most important feature is the moving map and airspace
limits and FLARM traffic view. Then maybe the final glide
calculation. I fly with voice variometer.