Ash is fabulous firewood. Dries fast, splits easily and burns nicely. I prefer it over Oak. They do become unsafe to climb more quickly than other trees in general especially if you need to do rigging off of them. They tend to rot at the base resulting in lots of leverage stress (I think because they tend to grow in moist areas although they will grow under many conditions). The wood that is up in the air is good for a long time. It has been a big bonus to the woodpecker population. Many pileated woodpeckers around now, a rarity in the past.