Honestly, I think the Stimpacks are a good thing - keeping players on their feet from encounter to encounter. As Genuine has wonderfully pointed out, Critical Injuries are where the fun starts and (after some experience in balancing) I'd expect my players to be getting injured with relative frequency - Combat is fast and punchy with huge emphasis on damage output and less on defence.
Players should probably look to end combat quickly and decisvely or else gtfo of dodge. Injuries are pretty good because keeping players hot footed in itself provides excitement - chases and daring escapes abound, or mowing down mooks, or the occassional unluck close call. But in an entrenched situation, they spice things up and hopefully get players thinking about an exit strategy.
Then once they're out of the encounter they can dose up to be in reasonable to face the challenges to come and take on more injuries! yum
Edited by SanguineAngel