I'd give it a 3 or 4 as well. It is hilly. But, it's only 37 miles. Stretch it out into 100 miles: that'd be a 5 (and 10,000 feet!!).

gadabout007: Not to say that Strava's power estimates are accurate or anything, but perhaps your friends weigh a little more than you? That would explain the difference in power output: they had to put out more watts just to ride with you.