I use them myself and hang them in file cabinets using the hangers stolen of regular cheap hanging files. My girlfriend figured out you can buy a box of hanging files at Wal Mart and take the hangers out of them and get 50 hangers for a quarter the cost of buying them from Light Impressions.
This system is much easier to access than books of sleeves or darn near anything else I've tried, and finding a numbered sleeve and putting it back is really fast. The important accessory to this is an index file of your negs describing what they are and what the file number is. I'm told Excel can do a good job here with search functions, cross referencing, etc.
Some people like the Print File pages. I never did in the smaller formats and I really don't like them for large format negatives. The negative has too much of a chance to be scratched during insertion and removal from the pages. I have been using the Interleaving Folders and Envelopes from Light Impressions for my 4x5, 5x7 and 8x10 negatives since about 1990. I wish they made them in 11x14 and 8x20 sizes also.