I have a GNS2000 since almost two years. It is rock-steady.
I use a Nexus7 (Kitkat 4.4.4) with GPS Bluetooth Provider (essential) and SkyDemon.
Lollipop 5.0.2 is not stable with SD, better stay on 4.4.4 or wait for 5.1 (imminent).
I also use a Lenovo Yoga2 10" tablet, reasonably priced, very long battery life (40+ hours), also available in 8" and 13.3" sizes.