As mentioned, it depends on the application. I've turned both hardwood and softwoods and both have provided excellent turnings, including pens. Most softwoods have open grain, as mentioned in replies above, which at times can be a nuisance when finishing, but overall, I've had pretty good luck so far. I've turned pine and yew, both stabilized and not. I prefer the stabilized softwoods as they turn and finish much nicer, and if dyed, provide some spectacular effects in the turned product. I try to stay away from wood with a lot of sap in it, unless it gets stabilized.
Paul