So, I bought a smart TV mostly because I wanted to stream local content to it and also upgrade to 1080p. But I also wanted to experiment with the HughesNet connection and overall smart TV experience. I'm posting my experience so far so that it may help others here and possibly prevent them from unexpectedly using large allowance amounts.
So here it is:
1. First off, whenever the TV is connected to the internet it is just like having any other device connected. It will use allowance, sometimes very little, sometimes very much.
2. When first setting up the TV you may want to try and do it during the Bonus/Free time as it will eat through data initializing all the apps and possibly doing a firmware update. I learned this the hard way as I did it during the day and went through almost 2GB. The firmware update alone was 800MB.
3. So once it is setup again realize it is just like having a computer connected. It may download updates in the background without you knowing about it. Even if you just visit the Netflix, YouTube, Hulu, etc., sites without watching anything, data is being used. These sites have thumbnail shortcuts to videos and they eat data. They may also be streaming advertising and short content clips while visiting. There is no way to block this that I know of like on a regular computer.
4. THIS ONE IS VERY IMPORTANT. If you do stream content from any site be sure to set the site to do it in standard definition if possible. If there is not a setting or you don't have an account to set it, you are going to be downloading at whatever definition the site defaults to. Usually higher definition like 720p or even 1080p. These definitions can eat through gigabytes of data in one hour. I personally have no problem with 360p on a 32" TV. Granted, probably won't be good on a 60" screen but be warned how much data true HD uses.
5. Finally, if you want to be sure to not use any HughesNet data while watching normal TV either turn off the wifi and/or disconnect the ethernet cable on the TV or turn off the Hughes modem.
That's it so far. Feel free to add comments and any further information I have left out.