The May '08 issue of the Nebraska Lawyer has an article on paperless offices written by Rick Jeffries. The experiences of the author were similar to my own when several of my partners and I started working on our paperless office several years ago.
Back in 2001, the municipal attorneys at my firm made the switch to a new computer system (from Windows to Mac--but that's another story) and decided that time was as good as any to begin working toward a paperless office. Within a month or two we were able to get all current cases scanned and organized but it took several years to get all our closed files pulled from storage and scanned.
The hardest part of a paperless system is not the hardware or software, there are a variety of scanners and programs, depending on your needs, to allow you to scan and index files. The most difficult part is actually making sure all documents get scanned and organized. Mr. Jeffries notes in his article that he uses Microsoft OneNote to organize his paperless files. Those of us in my firm that are paperless, however, use no special software. Instead, all mail is scanned and stored on the server upon arrival (and stamped scan on the back) before the attorneys ever see it.
All modern operating systems have built in search functions that, while not as powerful as a dedicated program like OneNote, can find terms in documents. With our scanning system anyone on any computer in the office can now search my files for motions, letters, terms or phrases.