Even without a data plan, blackberries make good devices for SMS conversations.
Note that you won't be able to browse the internet or download e-mail with out a blackberry plan attached to your phone service. Some carriers do let you e-mail to an SMS number like
and in some cases you can reply via an SMS and it will route back to the person that e-mailed you but you are limited to the 160 character cap of an SMS message.
The keyboard in my opinion is great you just type on it as if it were a full sized keyboard and ignore the strange letters it is displaying. When you space, it 95% of the time figured out what word you were typing out.