I've just completed OD, North to South in 8.5 days. I backpacked, staying on campsites or farms listed on the ODA list. All were near to pubs for evening meal or provided food in the case of the farms. I used the Trailblazer's guide which describes the route North to South, however some of the sketch maps in the book require a good imagination. OS maps are needed as well as some waymark posts are overgrown or missing. The book does have some very useful information for pubs, shops, B&B's etc.
It is not an easy walk, but I enjoyed it immensely, yes there are lots of stiles and plenty of steep hills to climb. There are some long sections of road walking and the bit between Llanymynech (beware the swans) and Buttington (beware crossing the bridge)is flat and boring. This is my first long distance path, so I can't compare with others, but I found it a great experience and worthwhile challenge. I was fortunate to have mostly cool weather in the middle of June, I would avoid attempting the walk when its hot, as there are some stretches where it is not possible to fill up your water bottle, as I found on my last day in 30C.