When I started racing, we moved next door to a pulmonologist. This was in Denver, often cool, usually dry. I came back from a hard MTB ride one day and asked my neighbor, "Hey, what causes this:" <WHHEEEEEEeeeeeezeeeeeeeee>.

She said, "Asthma! Exercise induced. How the hell do you race like that?" She brought home some gear and did a curb-side check on my flow before and during symptoms, and prescribed albuterol before any intense riding (any time I suspected I'd experience symptoms).

Albuterol has made a huge difference. Now that I'm in Austin, I only need it if it's cool and dry, but the dryer it is, the warmer I'll have trouble. I only seem to have trouble with intense efforts. It pretty much has to be intervals or a race equivalent. Tempo won't do it. Two puffs before a ride, and I'm good to go with no symptoms unless it's a really long ride. After 3 hours or so, I can start to have trouble again, but the albuterol kills it w/in minutes. I don't believe there is any connection to allergies for me.

One note that might be useful is how to take the dose. I see people all the time who are doing it differently than me. My neighbor/pulmonologist made sure I knew exactly how to take it, and checked back with me a couple months later to watch me take it again.
-Exhale fully, until there's nothing left, then exhale some more
-Hold the inhaler about 6" away from my wide open mouth, pointing in.
-Puff once, and about 0.1s later, start inhaling steadily, so that it takes 3-4 seconds for the full inhale
-Hold my breath until it's uncomfortable
-Wait 5 minutes, then repeat the above once

She said that it's best if every little pocket of my lungs is filled with medicated air, and the method above allows this. If you put the inhaler in your mouth, it's still wet when it hits the back of your throat. If you taste it at all, then that is wasted medicine that isn't doing its job. When I take it, I can taste a tiny bit on exhale, but nothing at all on the inhale.

I'm sure that some of you have used the attachments that make the harmonic tone when you're inhaling at the correct rate. These are great trainers for both distance and rate.