How do you define a hilly ride?

A friend was up visiting from FL last weekend and he brought along his bike. He wanted to do a couple of rides in the 25-35 mile range, preferably one flatish and the other moderately hilly. This got me thinking about how we define the hilliness of rides. I know ascents are categorized from HC to cat 5 but I didn't know if there were any broad classifications for total rides?

So I looked back over a year's worth of Garmin data trying to find rides that would fit his needs. This turned out to be a useful exercise and I ended up categorizing my rides by their hilliness factor :)

This is the formula I came up with for rides in the 25-60 mile range along with my avg moving speed for each class.

Flat rides: Less than 300 ft elevation gain per 10 miles: 20+ mph avg

Flat to Rolling: 300 to 500 ft gain/10 miles: 18-20mph avg

Rolling to moderately hilly: 500 to 700 ft gain/10 miles: 17 to 18 mph avg

Moderately hilly to Hilly: 700 to 1000 ft gain/10 miles: 15 to 17 mph avg

Hilly to Very Hilly: 1000 to 1500 ft gain/10 miles: 12 to 15 mph avg

In the end we did one ride that was at the high end of the flat to rolling class and another that was in the low end of the mod hilly to hilly class. Coming from FL, he felt the first ride was 'a bit hilly' and the second ride 'downright hilly' :)

How would these classifications compare to rides in your area?