While I actually haven't 'summited,' I've been up this mountain countless times (like most who've resided or studied in Boulder). Have yet to eat at the Flagstaff House. Awesome views of Boulder & the Great Plains from the roadside pullouts. My friend Uy & I scrambled up to the holiday star from the roadside one night years ago, slipping en route. That was fun. :) Would like to ride my bicycle up someday.
I have climbed Flagstaff several times. The first time, I climbed the trail, and then went straight up. You cross the road a few times. I have run/hiked to the summit a few times as well. You can just about see some of the snow-capped Rockies from the summit.
This is a fun trail for a quick after-work run. Watch out for cars though, as it crosses the road a total of 6 times. A more gentle and much less crowded alternative to the Sanitas Trail.