By the late 1960s everyone assumed solid-state gear would soon replace tube electronics, but here we are in 2011 and tubes are still here. Rock and blues guitar players still crave the sound of tube guitar amplifiers, and a significant number of audiophiles are die-hard tube fans.
While tube amps don't measure as well as their solid-state counterparts, some people feel tubes more faithfully reproduce the sound of voices and real instruments. As always, opinions about sound quality don't necessarily correlate with by-the-numbers assessments. We like what we like.