Forget about getting navigation from the carrier. Buy a smartphone and use that.
What are you looking for? I am a great fan of convergence devices like the Nokia N95, I got one because I need one now, have been using crappy LG and Nokia 'brick' phones for years.
Regarding the internet, that $7 unlimited internet is WAP mobile access, not high speed 3G network speed. Realistically, how much internet usage you need on the go? Messages/Data function is dependent on the settings you have on your phone, tremendous amount of information available how to setup the accounts, no issues there.
These are standard disclaimers.
It all comes down to your requirements (I won't say needs). BTW, I use the N95 on the pay as you go plan and use their internet as well, not a 'chatty' person though so its pretty manageable.