Car appreciation... the aesthetics, the engineering, etc

Nonsense.

They had to invent the harmonic balancer BECAUSE they were so badly balanced.

Wikipedia and everyone who has ever designed an inline 6 engine disagrees with you.

An inline six engine is in perfect primary and secondary mechanical balance, without the use of a balance shaft. The engine is in primary balance because the front and rear trio of cylinders are mirror images, and the pistons move in pairs. That is, piston #1 balances #6, #2 balances #5, and #3 balances #4, largely eliminating the polar rocking motion that would otherwise result. Secondary imbalance is avoided because an inline six cylinder crankshaft has six crank throws arranged in three planes offset at 120°. The result is that differences in piston speed at any given point in rotation are effectively canceled.
An inline four cylinder or V6 engine without a balance shaft will experience secondary dynamic imbalance, resulting in engine vibration. As a general rule, the forces arising from any dynamic imbalance increase as the square of the engine speed — that is, if the speed doubles, vibration will increase by a factor of four. In contrast, inline six engines have no primary or secondary imbalances, and with carefully designed crankshaft vibration dampers to absorb torsional vibration, will run more smoothly at the same crankshaft speed (rpm). This characteristic has made the inline six popular in some European sports-luxury cars, where smooth high-speed performance and good fuel economy are desirable. As engine reciprocating forces increase with the cube of piston mass, inline six is a preferred configuration for large truck engines.[6]

http://en.wikipedia.org/wiki/Straight-6
Perhaps you are thinking of torsional vibration? This is a problem in inline sixes because of the length of the engine is so long.