I've been using Netscape 4.7 for a long time now, all the while
knowing I shouldn't.  It mainly had to do with being familiar with the way
the browser behaved and wanting to continue my own particular style of
browsing.  Unfortunately, this also meant being thoroughly familiar with
the buggy Javascript engine that enjoyed freezing the whole browser up so
completely that it couldn't just be closed, it had to be killed from the
task manager.  And then there are all the HTML rendering engine problems, 
such as its inability to set frames to the exact size specified or its.... 
anyway, I'll just say it had lots of problems.  It was mostly inertia that 
stopped me from going to IE completely, plus it also lacked some of the 
things I could do in Netscape.
 
Now, though, I've switched to Mozilla, which has been a wonderful 
change.  The functionality is basically that of Netscape Navigator 4, but 
it actually works.... well, mostly.  It's a 1.1 version, so there are 
still a few bugs, but I haven't encountered anything on the level of 
Netscape 4.7's problems.  The tabbed browsing looks very interesting (you 
can dock different pages into the same window, letting you hit tabs to 
switch between them, similar to the tabbed worksheets in an Excel 
document), though I haven't made a lot of use of it yet.