This is a serious issue....battery. While the method I described above works great on both my iPad 1, iPad 3 and iPhone 5, I have noticed that my phone battery drain is quite noticeable. Since I'm retired, I have ample opportunity to change the phone but even with that, I wouldn't want to just leave VPN turned on 24/7. While the secuity isn't needed at home, the anonymity would be welcome (marketeers annoy me!) but I just don't want to be watching the battery all the time. I think with IOS7 and the easy control panel to turn off unneeded battery eating services it might be tolerable to leave VPN on all the time but not likely.
On the other hand, the larger battery on the iPad makes it reasonably tolerable. Ie, the ipad seems to hang in all day, even with the VPN on constantly.
Still, as you said, having the choice would be nice. LTE (and my grandfathered in unlimited plan) makes wireless sort of uneeded on the fly with the phone but sitting in hotels and watching Netflix or browsing on my WiFi only ipads makes having it available really reassuring.
Ah well, we'll have to see what IOS7 really brings.....but I can live with what I have if Apple doesn't break it!