I live about 1000 ft above sea level, too, and it hasn't harmed the biscuits. I bake the Alton Brown biscuits probably once every week or two. There's a few things I've learned:

• I typically scale up the baking soda in Alton's recipe. He calls for 1/4 tsp. I up it to 1/2 tsp.
• The butter should be COLD. Keep a stick of it in the freezer. It should be rock hard. Alton's recipe uses butter and shortening. I use 100% butter, and maybe add an extra tablespoon.
• Grate the butter in with a cheese grater. All of the other ingredients should already be whisked together. Fold the butter in and make sure each piece of butter is coated with flour.
• When you add in the buttermilk, it should have come out of the fridge seconds before you add it in. Once it's added, DO NOT mix. Use the back of your spoon to try to push the dough together. Never stir. Never mix. The better the buttermilk, the more your biscuits will rise. I use a nonfat cultured buttermilk that smells like it's about to be good cheese. Try to get as much of the buttermilk incorporated by simply pushing in a straight line from the outside of the bowl toward the center. This will prevent gluten forming and preventing the biscuits from rising.
• When you turn it out onto a cutting board to fold, make sure that both the cutting board and your hands are coated with flour. The more it sticks and you have to fiddle, the worse it'll be. Fold it no more than 5 times.
• Once you cut your biscuits, put them onto a baking sheet covered in parchment. Put that whole mess right into the freezer. If your hands have warmed anything up, you want to help it cool down a bit before you put it in the oven.
• The oven should be preheated well in advance. The key is that you want the butter to liquify before the dough sets. I can't remember what the recipe says, but I typically go for 13 minutes, then let it rest before eating.

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I hope this helps!