So I'll be switching shortly since we're starting a 3rd line and the new 10GB value plan will help us save about $45. It's worth it as even on my grandfathered unlimited plan, I rarely go over 3.5GB a month and the 2nd line only uses about 1.5GB.
1. Has it been confirmed that tethering is included in the mobile value plans? No additional fees?
2. I'm having a tougher time figuring out what to do regarding devices. I think the following makes sense.
Phone 1 - my wife's iPhone who is OK with 2 year upgrades. Switch to Next when the new iPhone comes out (assuming 32GB model for $818 after taxes). Pay the per month cost and fully pay off the phone. In 2 years, use the Next upgrade for the new iPhone and sell the paid off iPhone which should still fetch at least $350 due to their good residual value. Total cost of $468 every 2 years. Basically it's the same as buying it myself but at free $0 financing.
Phone 2 - my Note 3 with upgrades every year. What makes the difference is how the residual holds up as it's historically not as good as the iPhone or even the Galaxy S series (I always assumed since it's more of a niche product which hopefully seems to be changing). If after 1 year I can get $400 for my Note 3, then it seems to make sense to just buy the N4 for $763 after taxes, partially offset by the $363 in selling the phone (after swappa, paypal fees, and shipping). Total cost of $400 per year. If I only get $350 for the phone, then the cost goes up to $448 per year.
Going with the Next 12 plan, I'd pay $475 per year. It's probably worth some hassle to save $75 per year, less so to save $28 a year.
Phone 3 - going to buy a mint/new G2 on swappa for $400 and not upgrade it until it breaks.