Other rides that at least meet - and may beat - this ride in terms of challenge (just off the top of my head - I'm sure there are many more):
- The Death Ride (129 miles, 15,200' of climbing)
- The Shasta Summit Super Century (135 miles, 16,500' of climbing)
- The Everest Challenge (2 days, 206 miles, 29,035' of climbing)
- Brasstown Bald Buster (100 miles, 14,000' of climbing, ends on the 18-20% grades of Brasstown Bald, occurs in mid-May)
- Bridge-to-Bridge (101 miles, 10,200' of climbing, 85% of it in the last 45 miles)
- Garrett County Gran Fondo (126 miles, 15,500' of climbing, numerous climbs over 15%, at few over 20%, one over 30%)
- Mountains of Misery (103 miles, 10,000' of climbing [last climb very, very steep])
- Mountain Mama Road Bike Challenge (100 miles, 10,000' of climbing over 9 passes, some quite steep)
- Deerfield Dirt Road Randonée (a.k.a. D2R2) (112 miles, 16,500' of climbing, 70% on dirt roads)
Of these, the D2R2 is likely the most sinister - it has a 35-40% attrition rate. Brasstown is tough, especially given it's an early season ride. The Garrett County ride is nasty, and I can speak of that from personal experience. And the Everest Challenge is a lot of climbing in the course of 2 days.
That said, the Deer Creek Challenge looks like a good ride!