We used to do singletrack cycling on Cruisers long before people ever heard of mtbikes or suspended forks. We thought nothing of bombing down fairly steep hills on those things.
Today, I hear cyclists debating whether Cyclocross or mtbikes are better used for one type of off-road terrain or another. Personally, I still think that most Cruisers, Cyclocross, and HT mtbikes can all handle the same types of terrain in most cases.
However, I will make an exception to downhilling, which IMHO, should be reserved exclusively for FS mtbikes.
What are your thoughts?