Yesterday I just changed me & my wife from our AT&T legacy unlimited plans to a shared 10gb plan (think it's doubled to 20gb due to some promo). I think we'll end up saving over $30 a month and going from 1400 minutes to unlimited. I looked at the stats & combined in the past year our biggest usage month was about 5gb.
Not sure if you can look up the data usage on Verizon, but you can find it for AT&T. If your not using much compared to a capped pan & there is a savings, your probably better off changing.
I noticed the AT&T app now permits tethering to boot (not that it mattered, I'm rooted & running Cyanogen, so could tether natively, although in theory they could still detect that & do something about it, I never abused it though).