Thinking about a PDA phone

I am switching to a job where I will be working in a CIBC branch and I will be using a Palm to keep track of appointments/etc. I figured that I would switch to a 680 because I am already with Rogers. My question is do I have to switch to a data plan? I am already on a pretty good plan and was hoping that I could tweak it rather than start from fresh. I don't plan on surfing much and will mostly send text messages if anything at all. Also, does anyone know how well it performs as a phone? I am going to be replacing a Palm Tungsten E2 and a Motorola V635. Any comments are appreciated.