I've been using Motion-X GPS for about a year (Note that Motion-X GPS and Motion-X GPS Drive are not the same thing, the latter is for road navigation). I bought Motion-X GPS over Gaia because it is much cheaper and did everything I need it to. The app is $2, and that gets you the whole app except the ability to download custom map tiles (Google, USGS, Bing, etc can still be viewed but not D/L). If you want to D/L these custom map tiles, you pay a $5 in-app fee and it enables the ability to do so. However, keep in mind that the $2 app without the upgrade still allows you to D/L Motion-X Road, Terrain, and NOAA Marine tiles for free. Either way, you can max out the app's capabilities for $7, vs Gaia which is $20. Not bagging on Gaia, I think it's a great app too, but Motion-X GPS IS less money.
Motion-X GPS works great without any network connectivity. So well that I use the $2 version on my iPhone to map my runs as well. All you need to do is make sure your device is GPS enabled and that you D/L your map tiles in advance. If you have a 3G/4G-capable iPad, then you are already set with GPS as they come with the hardware installed. If you don't have a 3G/4G iPad, you need to get an external GPS transceiver like a Bad Elf. Downloading tiles is really easy, but takes some time and takes up a lot of space. I just checked my downloads and it looks like I was able to download Google terrain tiles for my entire state (down to zoom level 15, which is pretty detailed) for less than 6GB. I also downloaded the aviation sectionals for the whole state for 1.2GB. I usually use this app in the rig without any network connectivity in conjunction with a Ram mount and it works fantastically. That said, the app is not without its drawbacks.
First, you can't adjust the datum. WGS 84 is what it comes with and there's no way to change it. Not a big deal for most, but for me it is a huge limitation in SAR. Second, you can't set proximity alerts to waypoints. Third, and probably my biggest complaint, is that if you spin the map there is no natural way to reset north to up, other than clicking on the 'locate me' arrow button. So, if you're looking at the route ahead of you and want to reset north to up, it will reset to your current position on the map. Fourth, there's no road navigating, only straight-line navigating to waypoints. I get it, they have a road nav app they want you to buy separately, but it's a little frustrating that you can't even enable the feature via in-app purchase to make the app that much more powerful. Lastly, the app is built for function over form (bare with me here). It is not a very pretty app and the UI just feels old. That said, this is not necessarily a bad thing! An ugly & usable UI is much preferred to a beautiful and unusable UI, but a lot of modern apps have the best of both worlds so if that's important to you then it may be a consideration.
If I could go back in time and buy a new backcountry GPS/nav app, I would buy Motion-X GPS again.
