Carbs do fine at these altitudes. Especially SU's or ZS's, the DGV on my Cortina does alright too. DCOE's though, well they don't exactly like drastic altitude changes. Carbed engines do produce less power at altitude but so do Fuel Injected engines. The only true equalizer for altitude is forced induction. Which is why turbocharged front/all wheel drive cars are so popular in Colorado, that or Trucks/SUV of which still only about 25 percent see off road duty.
As far as personal oxygen use... /ubbthreads/images/graemlins/grin.gif Once your used to it, it's not that big of a deal. It's also easier living at 5,000 feet and going to 10,000 feet than living at sea level and going to 10,000 feet. Though when I travel to sea level I feel more energetic etc... with the boost in oxygen. Which is why the US Olympic Training Center is in Colorado Springs. High altitude training and all that. Another thing to remember if you travel to Colorado (or any other place with higher altitudes) is to drink plenty of water. With higher altitudes also comes less humidity and with every exhale you expel some of your own. A large factor of altitude sickness is dehydration. Of course there are different ways to stay hydrated. /ubbthreads/images/graemlins/thirsty.gif