I'm using Mozilla (1.6/Solaris at work, 1.7 RC2/3-WinXP at home). Starting to investigate the AdBlock plugin as AdSubtract is IE only now (also looking at Muffin as it would run on Solaris hosts too

).
Mozilla was needed for Solaris at work as it was talking to one of our MS portal servers better (they're using SharePoint and it uses NTLM Auth). Of course a newer version of SharePoint is now needing an ActiveX plugin which is NOT ready for Solaris yet.
For those curious why I'm going through such trouble, we have a number of people using diskless X terminals by NCD. They boot off a Solaris host (in our case) and connect via XDM to a CDE host session that was specified in config. No PC involved anywhere.