For 8 points and a gear slot this upgrade adds the ability to postpone 2 wounds until the end of the units next activation.
At 8 points Emergency Stims is quite expensive, especially if you are upgrading multiple units with them. 4 Emergency Stims costs more than a Bowcaster or an Electrostaff Guard for reference and often don't make up the attrition output difference because they aren’t extra health but postponed wounds. However for critical units like commanders and operatives it can be a valuable addition or even decide a game.
The best unit for Emergency Stims currently is any unit with Guardian, as they will often take extra wounds over the course of a game and can absorb additional wounds off of key units. Emergency Stims is also quite valuable on commanders and operatives or any unit who is high value and can greatly affect a game outcome with one last activation.
Han Solo Expansion, Boba Fett Expansion,