I would like to search my past text messages. I often forget which person I was talking to about the different issues and global search is helpful. Here is a picture of the equivalent functionality on the iPhone.
This SMS Organizer app has advanced search capabitilies.
It can search for any keyword, in the message content and also in the sender's name.
While you can search for all the messages in the "All Conversations" view, you can also arrange messages into folders, which can make searching and locating sms-es a lot easier.
For example, you can create a folder for all messages from a particular contact, so later you have to search in only that folder.