Diversions are a necessary evil. As a good friend said earlier today, "Life's just too short to worry about things that don't matter." I'm diligently working toward Halloween party things right now. I have looked at the ton of story notes I spewed onto printer paper. I haven't done anything more with my story. I think I'll consider this stage as the "percolation" stage of writing.
I'm allowing the story to roll around with a dozen other things in my mind. It seems like the kinks in plot or other inconsistencies often work themselves out if I force myself to wait a while. There was a time when I fought very hard to write every single detail in a super-special notebook that I would sift through when the time was right. I have several notebooks with practically irrelevant info now, with only a few gems among all the wasted ink.Ahem... I mean the important, brain-flushing idea-storms from which I gleaned true knowledge! :-\
While it's true that I often still make notes, I find that the more poignant details remain in my head and reverberate until something clicks in place, makes sense, and ends up a character trait, plot point or other significant bit of storytelling gold. I would be lying if I told you I never have moments where I should have written an idea down and felt it was deeply detrimental to the telling of a perfect story. :-D
Of course, a writer is only as good as her procrastination allows. Don't think that adding more details to your notes or doing a complete genealogy on every character will help you in the long run. When it comes right down to writing, planning is counter-productive and just another form of procrastination. Just start writing! I like this NaNoWriMo guy because he tells us to do just that.
And as far as detail while you're writing, be mindful of your tangents! Most of those little "darlings" you love will not fool an editor and you should be cutting them out in the editing process later. No matter what you've read or how self-indulgent the author is, know that what works for one author should not be a blueprint for you. As a reader, I could care less about the number of sparkles on Edward Cullen's forehead. Get to the point!