One of them took money out of each paycheck for a quarter and then gave you the better of the price of the stock at the start or end of the quarter. So you got a chance at risk free profits if the stock jumped. I was told that some people put their entire paychecks into it until they put a limit on the percentage of the paycheck you could put in.
The other one was a 15% discount off the stock price, again, done quarterly. Which doesn't sound huge until you calculate the annualized return. The annualized return on the first paycheck of the quarter was around 80%, the annualized return on the last paycheck of the quarter was around 3,000%. No lock up period and the smart thing to do would be to sell immediately and pay the short term capital gains tax.
I'm not smart, I still have the stock from that one. It keeps going up but it could also go to zero at any time. I don't want to pay the capital gains tax though. I should probably look at put options. First world problems.