I loved tabs in Galeon, it's the only browser I remembering having it at the time, but I probably didn't try Opera. I was sad when Galeon went away (or removed tabs? I don't recall) and I couldn't find another browser with tab support for a while. Again, I may have overlooked Opera :)
Galeon was also the only usable Linux browser having a native look on Gnome (Epiphany was the other one, but I remember it having more difficulty with a lot of sites).
It embedded the Mozilla engine (which was a supported use case back then, before Firefox) but launched a lot faster. Usable on a 200Mhz machine at least.
