Tablet - with mobile data or tether to phone?

For those who have tablets... do you guys have one with mobile data or just tether to your phone? I'm looking to get the Nexus 7 and don't see the point in spending $50 for the option to have mobile data and then another $20+ a month for data plan (I don't have shared data plan - I have unlimited Verizon 4G plan).

It's seems there are apps available to tether and as long as I'm not using the phone and tablet simultaneously, speed wouldn't be impacted?

Curious as to which is the better option to choose. Also, I know my unlimited data plan won't last forever, so perhaps getting the one with mobile data could be useful (so that if/when I go on a shared plan I can have my Nexus 7 join the party? Although, I suppose I could STILL just tether... no?)

What do you guys think?