Localytics has recently compiled some of their data through apps, and has concluded that only 6% of iPad sessions are made through a cellular network of some kind. They've also figured out that 89.7% of iPads out there are Wi-Fi-only, while 1.5% are the LTE-enabled new iPads. Even among new iPads, only 36% of the sessions are using 4G LTE. It's worth noting that the new iPad just went on sale in a lot of countries today, though other studies show that the U.S. takes up the lion's share of app activity.
These are some pretty interesting numbers, considering how much folks are concerned about blowing through their data caps with an LTE connection and a demanding high-resolution display. Small data buckets are likely a big factor in pushing people to using Wi-Fi over cell networks, and until plans improve, odds are things are going to stay that way.
The numbers seem accurate, at least in my experience. What about you guys - how much time do you spend using your cellular-enabled iPad outside the reach of a Wi-Fi zone?