I have grown it for two years with success here in Glasgow with no problems on germination. Good taste, very similar to butternuts. I think that the main use of it, is as a much better bet to mature than butternuts in the North. It sets the fruit at least a month earlier than butternuts.
However, Crown Prince is even earlier and easier to grow and mature.
Invincible is being touted as an improved Crown Prince. However, it is not nearly as sweet and does not keep well.