What are your likes/dislikes about the nerve agent auto injectors used in the military?

In the Sandbox we had a soon to be reduced in rank who decided to spray some Simple Green around which made the swabs go positive. Had 5 SMs stick their thighs with it before the laughter got too much. One had a major cleanup to do on Aisle 5.

To be honest, I've never had to use them, though I know of only 1 person who has (accidental)... Even though I carried them, they were out of sight, out of mind, except for when the horn sounded, so I really have no thoughts as to how to improve them or any real likes or dislikes... well.. other than that big a$$ needle... :D