I would get the 3G just for the GPS. The WiFi only version does not have a built-in GPS. You could get the wifi version plus the Bad-Elf external GPS. It will probably have a bit better accuracy but I like having it all built in.
I've read this in several places, but am seriously wondering if Apple has changed that. I bought Wi-Fi only 64 GB iPad-2 about a month ago (via Apple.com) and have since installed a bunch of apps, including ForeFlight. I also bought a GNS 5870 MFI Bluetooth GPS.
With the Bluetooth GPS turned off and the iPad NOT connected to Wi-Fi, I get no GPS/position/speed information. This is consistent when what I've read. Even the iPads that have GPS built-in have only "assisted" GPS that requires either Wi-Fi or 3G to get the GPS satellite almanac data.
With the Bluetooth GPS turned off and the iPad connected to Wi-Fi, I get GPS/position/speed information to an accuracy of typically 100 meters. This is the part that surprises me, but it's true, I swear! I can drive to a coffee shop in town, leave my Bluetooth GPS at home, and my position changes as soon as I reconnect to the Wi-Fi in the coffee shop. I definitely ordered and paid for the non-3G iPad. If anyone here knows how I can confirm for sure that I don't have the 3G unit (vs. Apple sending me a 3G unit even though I didn't pay for it), let me know.
With my Bluetooth GPS turned on, the iPad shows my GPS/position/speed to an accuracy of typically 10 meters, regardless of whether or not I'm connected to Wi-Fi (or 3G -- I don't have a 3G subscription either).
I've used ForeFlight in flight a few times now (so far only in Cessnas and Beechcraft), and I think I really like it. Reading the screen in direct sunlight has been easier than I feared (though the brightness must be turned all the way up). I used it at night as well, and since both the iPad and ForeFlight have a "dimness" control that are "additive" with each other (you can dim the iPad to the max, then dim it even more from within ForeFlight), you can dim the screen down very nicely. You can also invert all the colors on the display which can help further (e.g., draws an approach plate with white on black instead of the default black on white).
One problem I've had is accidentally changing screen views because my wrist or another finger touches part of the screen and the app reacts accordingly. You can "lock" approach plates but it really only locks the orientation. It'd be nice if it locked down everything except the "unlock" button, so that if you're flying an approach in bumpy conditions and/or in a cramped cockpit, you can pull up the plate you need and leave it there without fear of accidentally changing screens and having to try to figure out what happened while flying a critical phase of flight. I've had similar problems even on the ground, while planning a route using the VFR sectionals. On several occasions I've added lat/long user waypoints to my route without meaning to do so! An inadvertent touch of the screen can easily do that. But all in all, I really do like the app, and the iPad, and have been very happy that I spent my money on it (and Bluetooth GPS and ForeFlight subscription) vs. twice as much on a really nice Garmin GPS.
Oh, a few more quick comments on the iPad, ForeFlight, and the GNS 5870 Bluetooth GPS:
The iPad 2 has a couple of pretty powerful magnets in it for the optional cover (which also has magnets). They don't seem to interfere with the built-in magnetic compass capability of the iPad (how do they do that?), but they could affect the magnetic compass in your aircraft. Check it out in your plane with the iPad situated where you'll normally use it in flight.
ForeFlight doesn't show you the chart legend, so you need to look up a symbol you'll need another source. It does mark airspace hours however -- tap on a restricted area and it'll tell you the days and hours that it's hot (transferred from the end panel of the sectional, which you can't access in ForeFlight).
If, in ForeFlight, you zoom in enough at area where a TAC exists (such as KSEA), the TAC is displayed instead of the sectional, which is really cool. However, this is only true if a separate TAC chart exists. For areas like KPDX, where there is a "mini TAC" for just the Class C area on a chart panel (paper sectional), you're out of luck with ForeFlight. No matter how far you zoom into KPDX you get only sectional data.
I'm still looking for a good app that will store my flight track for later review on Google Earth, etc. Advise if you have any recommendations. I wish ForeFlight would do it.
I love the Bluetooth GPS. Throw it on the dash or stick it to a window with the provided suction cup and away you go. No wires whatsoever, and since both it and the iPad have 10-hour batteries, you're set for a whole day of flying. However, the GNS 5870 is turned on and off not by a physical switch, but rather through a "swipe" of your finger. It's easy to accidentally turn it on while sticking the unit in your pocket and run down the battery. It'll auto-shutoff if there is no Bluetooth connection for 15 minutes, but if my iPad is within 25 feet or so of me, I'm hosed, as the Bluetooth connection will remain. Also, sometimes the "swipe sensor" doesn't respond (my finger isn't "human" enough???), and I have difficulty turning the GPS on or off. I may consider buying a different Bluetooth GPS, which has a physical on/off switch.
OK, sorry for getting carried away. I do love my iPad though! ;-)
