I've had the Premium Plan on my Verizon phone for almost 2 years. I text a lot... check my email... check the weather... check news... use VZ Navigator 2-3 times per month (some times for a couple of hours at a time -- make sure you have your charger it uses a lot of battery)... and use the phone moderately for calls.
[Hint: if you don't think you'll use VZ Navigator, go to one of the Select Plans... save yourself the money)
In about 22 months of use, I've never had a bill for more than the plan price (plus taxes and local fees, which you have no matter the plan). However, I never go over on anytime minutes.
The premium plan capable phones do not have continuous data apps (i.e. you have to tell the phone to show you the weather, news, email) and I find I don't use that much data on them.
Now, that said... i'm in the process of looking for a new phone and deciding if it's worth the extra $20 a month for a data plan for a droid or blackberry. I'd love to have my email automatically delivered to my phone or just be able to look at my phone to have the weather or a news feed. However, I'm not sure it's worth the extra cash.
