I have the 4.3" Navigo with a quarter mil memory map installed.
Pros: Cheap, works OK, MM can also be run on home PC for map browsing
Cons: Screen too small, less than 90 mins battery life, zoom steps are awkward
Although it was fun to tinker with, I've gone back to my ageing Garmin 195. Personally, I don't think the Navigo is a viable proposition for safe use in flight due to the small on-screen buttons and the shortcomings listed above.
OK I suppose, if there are 2 pilots on board or to entertain the passengers, but I couldn't recommend it as a serious nav aid.