I did this week. I discovered that I could really enjoy trail running by accident. Lunch time run at work,planned what I though would be a 4 mile run (road and park pathways) ended up running 6.5 miles with 5 of those miles being country path ways/right of ways.
On the map, the route took me through a park, it was much tougher terrain and much more natural wood than I though. I lost my way, stressed a little, but stared to enjoy not knowing where I was!
I dont think this is ideal training, but it makes for a fun run.