As applications go, Day One is really starting to move up the list of my most-used applications. It's the first application I load in the morning, as I use it to write my Morning Pages and it's one of the last applications I use in my day as I document what has been achieved, write about anything special that has happened as well as planning out my most important tasks for the next day. I've even got an action created within Drafts that will pass my text straight through to Day One, allowing me to stick with my theme of simplicity and use only one application for inputting text into my iOS devices where possible.
One other use that has really started to develop over the last month has been during my daily role as a contractor. I'm working as an IT Project Manager currently and Day One is an ideal tool for capturing information for adding to my Daily Log . Information I capture includes summaries of conversations with people, tasks achieved on any given day, meeting minutes, webinar summaries, dealings with third parties as well as more standard information like mileage, expenses etc that need to be reimbursed. It really does function as my contracting diary.
I use Markdown to create my contracting task list that I work from, with MITs in the top section of an entry and a wishlist of tasks to be completed below. As I work through them, I mark them as bold when they are actioned. Filling this list really is as simple as right-clicking actions from OmniFocus 2, copying and pasting into Day One. I also use lots of different tags - Daily Log, Issues Log, Meeting Minutes, Conversations as well as individual people's names when it involves them. As you can add multiple tags to an entry, it's very simple to retrive information when you need it. That's the key to any good filing system - ease of retrieval.
When my client needs information regarding an update on any given situation, Day One is now referred to as well as DEVONthink Pro Office, OmniFocus 2 and OmniPlan. I never thought that would be the case with something that I had always assumed to be nothing more than a diary application. With some imagination, Day One can be a powerful weapon in your productivity arsenal.