Yeah...only data plan. I have two other lines for phone usage. I prefered the data plan only. Just today a friend and I were talking on the phone and asked me to check something. It was much easier to hold the phone with one hand and the other to browse the internet instead of saying "Hold on. Let me check." lol. But that's just me. I know a lot of people wanted to converge their voice and data and are extremely happy and stress free because of that decision.
I am primarily using the curve for e-mail and internet. It's an amazing thing to be on the golf course and respond to e-mail or check something for someone. Also, it was exhilirating experience to be at a bookstore and asking myself, "Hmm...I wonder if this is a good book. I wish I could check the reviews on amazon.com. Oh - that's right. I can!" =)