This seems like a massive upgrade over regular nutrients, would you say its balanced (not even that its equal, but comes with any kind of cost) by any added mechanics or is it just a straight upgrade over biochambers?

In terms of "yummy" value (fuel value) for the alt recipes, slurry is supposed to be balanced with regular nutrients and bioflux. The main advantage of slurry is that it never spoils, at the cost of some additional crafting complexity (water, ice, bulk nutrients by the hundreds). I'm open to balance suggestions; configuring different difficulties in the mod settings wouldn't be very hard I think.