We have an iPad 4 with Garmin BlueCharts as our 3rd level of chart plotter.
Our primary chart plotter is an HP lap top with Open CPN which can drive
the autopilot and display the AIS targets. Cristina has a Dell running Open
CPN.  The iPad is great for a rapid look far down course  and  for rapid
zooming  of hazards and anchorages(I do not find it as easy to use for
route planning, so I rarely use that function.).  We find it nice to have,
but not a got to have.  We also use it to access Google Earth  as others
have commented

In the dinghy we use iNavX on an iPhone5.  We do range very far and wide in
the dinghy often over ten miles from our boat. iNavX is adequate for that
application, but I took it off the iPad in preference to Garmin BlueChart.
Tom
Tadhana
Deltaville VA

For those of you using a Windows PC to run Open CPN, Coastal Explorer, or
other PC options.  I would recommend a look at the MS Surface as a tablet or
one of the ASUS, Lenovo tablets.  I am using Rosepoint on my nav station PCs
with SiTex AIS and NMEA2000 instrumentation.    I can plug the CE dongle and
the NMEA 2000 into my Surface docking station and the Surface works just
like my mini desktops.  The multi-touch stretch and zoom make it easy with
CE.

Henry Dennig
m/v Seven Tenths