I’ve had a few paralever airhead GS’s, paralevee airhead PD’s, late ‘hex head’ oil cooled 1200’s, even a couple SWB 750’s. I will say generally that any flat twin is not a romantic sounding or feeling engine, and they are best kept well muffled, the one ‘91 Bumblebee I airhead I still have I bought new in late 1990, now 238,000 kms, still original engine, clutch, but 3rd drive shaft. Has been to Baja, Key West, would ride it anywhere tomorrow. The 08 1200 hex gs I bought late ‘08 with 7,000 kms, now 125,000, all original everything except factory recall on fuel pump/fuel gauge sender strip, a result of effects of 10% ethanol which effected the copper sender strip on the guage. The engine power lifts the front wheel in 2nd gear at 70km hr if I turn the traction control off. Gets 55 mpg , extreme comfort, grinds the outside of my riding boots way too easy, go through a pair every couple years. Corners easier than my RC30, calmly does 100’s of kms remote gravel at 120 km hr.
Yeah for sure they are ugly, and different ADV bikes and dual sports all have different versions of falling out of an ugly tree. But we have Laverda, and BMW to thank for starting a motorcycle segment that arguably is the most popular segment in motorcycling today, excluding tiny bikes and scooters.