Spivak pronouns have all the benefits of a singular "they" with all the drawbacks of introducing a new set of pronouns into an established language. My experiences with programmers tell me that getting a large group of people to change syntax is not easy.
Spivak pronouns do indeed come with drawbacks (as do all proposed solutions for gender-neutral language) but I put forth that said drawbacks are minimal. The pronoun set is intuitive to English-speakers and I've found that brief explanation, if any, has been required no more than once per person before they can easily grok my usages.
I agree that from a perspective of getting more people to use them the drawbacks are greater but from the perspective of understanding the drawbacks are essentially non-existent.
I agree with you: Spivak pronouns are definitely easy to understand. I just see getting more people to use them as key to having a standard third person gender neutral pronoun in English.
