Another potential gotcha is the post-IPO sales lockout period. I don't know if it's the same in software, but in a previous life I was a chemist in a biotech startup that had an initially successful IPO. The rank and file were prohibited from cashing out options for six months after the IPO but somehow all the execs were exempt and got rich while the stock was enjoying a post-IPO high. Needless to say, by the time we peons could sell the value had plummeted.