Chaotic has it nailed. It is a TREMENDOUS benefit. Helps you relax, and focus like you wouldn't believe.
I've tried dozens of different plugs. The best comfortable examples I've found are called Howard Leight brand, Max Life. Green colored foam.
I just did a 2,400 mile trip to Arkansas on my FZ1, and it was very comfortable.
I have many in my truck as well, and hand them out at the track. I've converted many into believers.
'12 Triumph Daytona 675R
'06 Yamaha FZ1
'04 Yamaha YZF-R6 (Track bike)
'03 Honda GL1800 Goldwing
'01 Suzuki DRZ400S