I use 7 day moving averages together with 5th degree polynomials to keep track of things - I haven't been at this long enough to perform any meaningful statistical trend analyses, so I use my data to mostly track my progress for the time being. Here's my summary chart:
(http://www.strathdee.net/temp/chart.jpg)
As far as overkill is concerned, I don't think it is. I'm in this full time, and I'm not going to depend on chance or luck to be successful. I think it is completely necessary to be as informed as possible about the state of my income.
Or at least as informed as my puny brain will allow.