I''m not training for anything specific but I ride 1 1/2 hours every morning at a rate that causes me to be uncomfortable at the end and then ride 6-10 hours one day in a weekend. I also commute 1-2 hours every day on my bike as well. In terms of conditioning its great. Not in terms of speed as such but I can ride all day and not even feel it.
As for its value? Pure fun.