Just switched to T-Mobile last month: much better experience than what I had with Verizon so far.

There is also the option of individual data plans (per line) that include this flag as well, but they of course cost more. Example: You get $30 for 2GB on Verizon, but to enable the mobile hotspot you need the $50 for 4GB plan. In AT&T's case you would need the $50 5GB plan to enable mobile hotspot.

In the case of Verizon, you're perfectly able to download a third party tethering application (as per the FCC ruling) and use it on their old tiered individual data plans. If you have Verizon's grandfathered unlimited plan, you are able to add on the $30 unlimited tethering option as this plan did not fall under the FCC fiasco. However, I have not heard of Verizon going after anyone using a third party tethering application on an unlimited plan. It's worth noting that Verizon is still the only carrier that ever offered and still offers (to subscribers that already have an unlimited data plan) truly unlimited and unthrottled tethering as an option as their LTE network is not throttled.

In the case of users still on AT&T's grandfathered unlimited data plan, they are throttled to 0.5Mb/0.5Mb after 3GB for 3G devices, and 5GB for LTE devices. They also will automatically move you to a tiered plan if you attempt to use any third party tethering applications and do not offer any legitimate way to tether on this plan.

I'm hoping that one of T-Mobile's next moves will include adding unlimited tethering that is unthrottled to their unlimited data plan.

Which is ironic, as tethering is the only context in which I would come anywhere close to using up my monthly bandwidth allocation.