Having internet always available on the iPad truly is a killer feature that I was taking for granted...especially with LTE. While I always had tethering enabled on my phone to do this, the tethering always took time to setup and was kind of clunky...not to mention that the speeds weren't exactly blazing. I used my iPad on the train most of the time offline and didn't bother to hook up the tether.
Now my iPad just always has internet. Whenever I want it.
My biggest beef with all the radios this thing has is that it sometimes fights itself trying to find the best signal. If LTE is weak, it'll randomly drop LTE and go back to 3G, then flop back to LTE...somehow dropping down to sub-3G at points, then up to 3G, then up to LTE. It's better in some areas with weak LTE to just turn off LTE all together and just work with the rock-solid 3G to prevent all this.
The problem with all that radio swapping is that the iPad acts like it has no internet while it's transitioning radios, so you'll get a "no internet" pop-up and then dismiss it only to have the page reload itself anyways now that it's got a connection on the other radio.
Needs to be smoothed out a bit, but I'm guessing that that's just the way it is and the only way to make that less painful would be to literally have LTE and 3G bands connected simultaneously so you can hot swap to one connection or the other automatically without dropping connection to transition (but god knows what this would do to battery life). If there was a setting to never jump on LTE unless it was at least 3 bars of strength or something that'd be ideal, given the current implementation.