Well, if you dont plan on tethering and dont plan on using an Exchange server, then all you will need is the $30 forced data plan.
But if your like alot of "power users" (like me), then those features are kinda necessary. I need exchange for my work email, and I also need to be able to tether. Although I hardly tether, there are times when I have to remote some servers when I am on the road, and free WIFI isnt always easy to find
Honestly, VZW should just have a flat rate pricing. I mean what justifies the extra 15 bucks for Exchange? Why not include all of those features in the 30 data plan?.