> I would strongly advise everyone to max out their ESPP contributions (you can contribute a maximum of 15% of your salary, up to the IRS mandated $25,000 limit).

IIRC we used to be able to contribute more than 15% of salary. I recall nearly doubling my base salary in the late 90s by putting something like 25% in. That was a particularly sweet ESPP in that they set the price to be the lowest in the last 2 years. Now I think it's always the lowest in the quarter or half that you're participating in so not nearly as lucrative as it used to be.