Just looked up the stats from W3C, which I am sure we will agree is a reliable source, and the last stats they have for NS3 were back from 2004 which shows inbetween 0.2% and 0.8% of Internet users using it.
After that stats arn't available as I belive the use dropped to negligiable with the release of Mozilla and the Firefox.
Considering were now in mid 2007 I doubt anymore than 0.01% is using it - therefore I wouldn't count it as widely used!
.
Also considering usage of Netscape 7, which is 4 versions later than NS3, in 2004 was only 1.5% at its peak it shows that even the later versions of Netscape arnt widely used.