Traditional, top-down professional development (PD) can render teachers mere implementers of the ideas of others, but there is some hope that the participatory nature of social media such as Twitter might support more grassroots PD. To better understand Twitter's role in education, we conducted a survey of K-16 educators regarding their use of the microblogging service for professional purposes. Respondents described multifaceted and intense use, with PD activities more common than use with students and families. This paper delves into qualitative data from 494 respondents who described their perspectives on Twitter PD. Educators praised the platform as efficient, accessible and interactive. Twitter was credited with providing opportunities to access novel ideas and stay abreast of education advances and trends, particularly regarding educational technology. Numerous respondents compared Twitter favorably with other PD available to them. Members of our sample also appreciated how Twitter connected them to educators beyond their own schools and districts, with mention of exposure to both like-minded and diverse perspectives. Respondents described positive and collaborative professional activity facilitated by Twitter, and many noted how it helped them combat various forms of isolation. We conclude by discussing implications of the survey results for educators, researchers and policy-makers.