In general, when it comes to keyword stuffing, normally the max amount of keywords that you want to put in a post is 3 keywords. For a post that is under 600 keywords, only use your primary once and your secondaries once, anything over 600 words you can do twice. That has been my rule of thumb and I have had no issues with getting slapped by penguin, panda or any other cuddly algorithm updates. In addition, as I read before, a lot of the onsite has not changed.
Because of the algorithm updates there was a scare that you can over optimize, and yes you can. But that is only the case when the user experience is no longer there. If you write for SEO and optimize for SEO but the user has no idea what they are looking at, you are going to get slapped, either by robots or by a manual review of the site. Just be sure to backlink appropriately, normally contextually. You will be good then. Hope that helps.