"3G" iPad required
Yes, you need the "3G" variant of the iPad (to get GPS functionality) but it typically loses connectivity at some point on pretty-much every flight. As such, I use MemoryMap/iPad combo only as a planning aid/toy (my Garmin GNS430 does the real work in-flight).
For what it's worth, in my opinion the iPad truly comes into it's own in the cockpit with Jeppesen "JeppTC" software. That is the sole reason I purchased an iPad...and it would still be worth every penny if I had no other software or use for the iPad. I used to subscribe to Aerad "Touring Guide" for IMC/approach plates, plus the usual plethora of VFR flight guides. All that paper now gone with Jeppesen JeppTC plus VFR and IFR subscriptions. Expensive but you get what you pay for. Moreover, the routine updates are seamless and automatic (one click) -- no more messing about on Sunday nights sorting out printed amendments...
All that said, the iPad/MemoryMap combination is still fun but really not a serious piece of kit...