I've done it. Mostly, i ignore the 'update soon!' stuff. By this, i mean, if i get a comment that says 'yay, loved this chapter! when will there be more?!!!!' I just say 'thank you, so glad you enjoyed!' and utterly ignore the update part.

Then if i post again before i have more of the story, i say something like 'chapter next up in a few days!' or whatever. I like to have my stuff out in a timely fashion, and haven't done a *lot* of WIP with big gaps or anything, but i don't have massive guilt or anything, either.