La Ruta is hard no doubt about it. Several factors make it a very challenging race:
1) The Costa Rican riders are very strong. Not just any local can compete, they must do well enough in a qualifiying event early in the year which to the best of my knowledge is the same course as that of day 2.
2) The conditions. It can be extrememly hot and humid, there can be some intense rain storms, and insane mud. On the top of the volcano on day 2 it can be freezing cold. I think several Europens had to drop out on day 2 in 2001 because they were hypothermic. As would be expected, the mud can wreak havoc with race plans.
3) The course. There's not much single track but there's plenty of double track and very steep sections. The total elevation gain over 3 days varies from about 23,000-28,000ft.
Unlike other some of the other popular big races such as the Transalps, Transrockies and Cape Epic where you have a day or two before the hard stages, day 1 at La Ruta is the hardest stage. Most people drop out on day; there's usually a 3/4 finish rate. The race never gets easier. Any changes that Roman, the race director, makes usually means more time for punishment. I have great respect for anyone who finishes that race no matter their placing.
I'll be doing La Ruta for the 4th time this year.
This link has a few "interviews" with racers I know, like Sho-Air's Manny and La Ruta Lou, that has some of their thoughts on how to approach the race if you are gonna race it.
http://enjoying-the-ride.blogspot.com/1990/01/notable-posts.html
Here's the offical website:
http://www.adventurerace.com/eng/english.htm