Intel suggests running it once a week which takes about a couple seconds.
Not sure if it does increase performance but it does seem to effect the Win7 WEI score for some reason. You can test this for yourself and see. After Win7 install and running the optimizer do WEI and either do a screen capture or write down the score of your ssd. Don't run the optimizer for a couple of weeks then refresh the score. Most likely the ssd score will drop somewhat. Then run the optimizer again and refresh the score and it should climb back up....Well at least that's what it does on mine so I just try to remeber to use the optimizer once a week or so just in case.
Here is a link to the intel pdf white papers on the SSD Optimizer that explains exactly what it does and how. After looking at it I guess it makes sense why the WEI score would degrade then rise once the optimizer is run.
http://download.intel.com/design/flash/nand/mainstream/Intel_SSD_Optimizer_White_Paper.pdf
After looking at the pdf again it looks like it can just be scheduled to run without any intervention. Just set mine up to run every Friday at 7am