Useful if you want to view the investment potential on a share (i.e 50 to 100 is double and 100 to 200 is doubled again). For other analysis I have never bothered and it seems to make things more complicated than it needs to be. I would make an exception in the case of long term charts. For example looking back over 100 years on the Dow makes interesting viewing on log charts, as does the last 20 years of the Nasdaq.
