The first "real" road bike I owned (Bianchi Limited, 1986-ish) had
downtube shifters and I've always had at least one bike so equipped
since then. In my long range plans for a custom rando bike, it will
have downtube shifters. My daily commuter has friction DT shifters, as
does my Trek 560. I also have bikes with thumb shifters, a Bontrager
mtb with grip-shifts (hate those but haven't taken the time to convert
yet), and a cross bike with brifters - whose only advantage I can see
is when I race I really can shift quicker. But those buggers are sure
expensive to replace and I hate components I can't service myself.
Strangely, the only thing I don't currently have running is bar-ends,
but that's going to change when I get the dirt-drops on the 91 MB
2 ;-)
As others have said - though maybe not here, one advantage to DT
shifters (besides simplicity) is that on longer rides you regularly
take you hands (or one hand at least) off the bars. This helps relieve
pressure and fatigue, I think.
And maybe it's how I was "programed" when I formed my love for the
bicycle, but I prefer the look of a steel road bike w/DT shifters to
the look of any other bike.
Mike