Dr. Naomi Nascimento, a computational linguist who holds a PhD in Linguistics and an MS in Physics, uses Day One as a research journal:
I used to keep [my research journal] in MS Word, but the file would get unwieldy, and trying to keep multiple copies of it was difficult. Now, I can write in my research journal wherever I am (on my iPhone), then flesh out my notes written on the run on my Mac. I even stopped in the middle of a jog in the park this week, pulled out my phone and added an entry about the research idea I had while running. I use it to keep notes of conversations with colleagues, experimental metadata, and use the camera to attach photos of white boards after a discussion, or import a figure I created or a figure from an article I’m reading.