Opera in the late 90s / early 2000s was excellent. It was lightweight and snappy. Among the first to support tabs. The Presto engine was the most performant on machines of the era. The trialware/adware was annoying, but the browser was solid. The built-in email client was decent as well.
In 2009 they launched a very interesting web server / sharing feature with Opera Unite, which unfortunately didn't gain traction.
Opera Mini was the best mobile browser for a few years as well, before smartphones took off.
