My Mom has a blackberry 8220 with no data plan. It's a great phone with her because I can take care of her contact list on the computer using Outlook and be sure she has everyone listed that she needs. It is easy for her to use and can change the fonts so that it's easy to read the screen. She even started using text messages after she got this phone so we did add feature enabler so she could als send/receive messages with photos. But she has no desire or want to use it for email and internet browsing. She just likes it as a phone and it works well for her.
I can't imagine not having the data plan on mine because I like my email. I could live without my internet but the email has spoiled me. But Mom certainly doesn't need it. (Heck, she doesn't even read it on the computer every day.)
Personal: iPhone on AT&T
Work: BB 9650 on Sprint