Hi Jennifer,
I know this is waaay late in replying to your original post, but I think it's still relevant.
We have used text-to-give, but it's not something we are focused on. We've never seen text-to-give take off as a viable option for ongoing fundraising. I think a lot of nonprofits have experience this, too. Text-to-give is much more effective for emergency response, such as natural disaster relief.
That said, text instead could be useful as an engagement tool. Send the user/donor info about upcoming events (or follow up with a link to pictures from an event), that you sent out the latest enewsletter, their sustaining payment went through. Just little updates and/or reminders to keep them aware of and engaged with the org.
Hope that helps a bit.
#FundraisingandDevelopment