Honestly I see very few liabilities in traveling by 125. I've found I have plenty of power to get up the mountains. Yeah, I can't climb 'em running 70 MPH like I could on "big bikes" but it's not like I'm pushing. I more than make up for it coming down the other side.
It's more of a mental adjustment than anything.
When I found myself no longer wanting to travel the autobahn and spending most of my time on back roads suddenly the idea of riding a 650 seemed kind of silly when most of the time I was cruising at 45-50. All of a sudden riding a 175 lb. 125cc bike made a lot of sense.
It ain't for everybody but it works for me. When folks figure this out and realize bigger ain't always better we'll see a demand for small bores again.