My brother and I rode 104 from Tucumcari to Las Vegas (7/18/12).
This road has awesome scenery especially coming from the TX, NM prairies.
This is mesa country and you ride between and among the many mesas, cliffs and canyons here.
Eastern NM has many plateaus and when you drop off one, or climb up to the next, the road cuts through fantastic canyons and rock formations often switching back to make the route.
The last 15 miles into Las Vegas open up and provide distant views of the Sangre De Cristos to the west and north.
We could see distant thunderstorms and their rainshafts across the plains.
I advise filling your tank in Las Vegas or Tucumcari as the only services are at Conchas Lake (if open) and there is 75 miles of nothing but pavement and views from there to LV.
Iíd rate the quality of pavement at about 6 or7/10.
As a Midwesterner who rides Michiganís notorious pavement, I wasnít impressed with the road quality in NM.
Don't let that stop you though, I am riding on 1983 suspension technology Ė you probably arenít.