Treo 750 Threaded SMS
I'm not a big SMS guy, primarily because my brain doesn't think well in T9 mode. Palm made SMS on the Treo 750 more like an instant messaging client, by making SMS conversations threaded. I love it. I can send a message, respond, get a response and follow the conversation even if the messages are several hours apart. Having a full keyboard gets me to use SMS, having it work more like email or instant messaging with conversation tracking makes it easy to follow what's being said. You get a SMS thread for each conversation you're having. The one trick I noticed in this is when someone you message sends a new message instead of replying. The new message starts a new thread even though the message was really part of the previous conversation. I'm chalking that up to a limitation of SMS at this point, but hopeful Palm can figure out a way around this in the long run.
Below you can see an example of a threaded conversation.