I used to do it on the bike with good results (15 minutes: 10 seconds all out, 50 seconds idle peddling).
I like sprinting up hills too. The problem I have is I always go all out, absolutely to the max, and it's miserable. I have a hard time sticking to it because it's so brutal, and I usually would do it on my "off" days, but the cardio workout was harder than my weight lifting workouts!
Does anyone else have a similar problem? Do I just need to hold back a little, or am I just a bitch? How many days a week do you guys do this stuff?