i'm aware of player effects, but it doesn't meet all my use cases. one of the biggest differences is that a single effect created w/ status effects can be used simultaneously by multiple separate mods without explicit integration code. this allows you to e.g. have a player be poisoned from two separate sources, and have the amount of the poisoning stack. you can also have, say, an "antiserum" that cures the poisoning from all sources, though it looks like player effects does allow cancelling an ongoing effect
another difference is that it's possibble to define an effect which increments or decrements a value every-so-often (e.g. poison or regen), and have the effect "catch up" if there's a lag spike.
for uses of status effects, see std_effects, which i'll add to the CDB when it's in a more finalized state. in particular, the exhaustion, lycanthropy, and builders_flight effects should show some of the power of the approach i've gone with. you can test out this mod (and others) on my public server "fluxtest" to get a feel for how effects can combine.