The large flat panel multifunction displays that run on NT use a stripped-down version of NT. Stuff like printer and network support are stripped out, as are the countless services, plug & pray, etc.
This should be very reliable; NT3.51 was one of the most reliable bits of software around.
Most of the reliability issues come from badly written applications; unsuprising since most PC users think they are entitled to throw any piece of PC software at it (and they aren't wrong).
I think that about £200 of the price of a typical aviation GPS is the Jeppesen database. If Navbox used Jepp VFR map data, its price would rise from £60 to probably £300.
The tablet market is changing rapidly too. The performance has been there for a while; they need to get thinner and lighter, and dissipate much less heat.