Netscape 6 is basically 100% standards-compliant, but also amazingly tolerant of non-compliant HTML. If a page that worked in IE5.5 doesn't work in NS6, that's the webmaster's fault for going over-board with IE-specific "features".
And NS6 starts slower than IE because IE is basically integrated into Windows, a happy side-effect of Microsoft force feeding you IE. When you start Windows, you pretty much start IE. Makes me wonder if Netscape couldn't do something similar.