We have Penstemon Digitalis put in by a landscaper 10 years ago. It has spread all around our yard. It is easy enough to pull up, but it flowers so nicely (and well above most of our other flowers) and stays at the edges of beds, so we just leave it.
Where I lived before they were mildly invasive, but I liked them. Where I am living now, it is not al all invasive, as a matter of fact I am worried it is not going to reproduce. I think I have the same plant for three years now and not one new one!? Oh, well it will do what it will do and I will not worry about it. I do like them though. Esp the dark red leaved ones with white flowers --- Really sharp lookin'!