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.