I'd say absolutely worth it, but it's worth bearing in mind updates are released sparsely and very slowly. However, it seems the quality, thought and soul is always there despite the time frame. Though these aspects aren't inherently mutually exclusive with one another.

For example, if you're into ASOIAF and can't bear waiting 10 yrs for a sequel - but the journey there is gold, this has similar vibes.

Look at is as it, for all we know they might abandon it, anything can happen during early access BUT it's fun, great alone or with coop and free from the plague of practices which mire 'modern gaming'. Enjoyed my time with it absolutely.

Edit: Also keep in mind what you feel comfortable endorsing with the money one gives, reflect on the company and the product and come to a conclusion you're comfortable with