In actual play however it's been one of the safest and easiest games we've ever played. In both ours and the online game there's not been one PC death, and only one Comrade has died (when I was guest GMing in our campaign).
There are a number of reasons for this, both mechanical and psychological.
From the mechanical PoV:
- The system has what is basically a D&D Style Hit Points (called wounds, typically 12 points or more). Until these are gone, your character if fully effective and 'safe'. This combined with the damage reduction provided by Toughness and Armor results in a very significant Buffer against common weapons. A well built and moderately equipment character can soak *a lot* of hits or even become all but immune to less than Heavy Weapons fire.
- The Logistics System allows characters to quickly attain high end armor and weapons further increasing their ability to suck up incoming damage while increasing their outgoing damage to levels opposing NPCs can't handle.
- The mechanics for teamwork and leadership are well done (i.e. they are suited to the genre and effective), however they amplify the above effects significantly. In any battle the PCs will defeat equally (and even better) skilled and equipped opponents due to the effect of these rules.
- If you do get into trouble, Fate Points will generally get you out of it.
Now naturally the GM is capable of throwing powerful enough foes at the characters to overwhelm them. However it's impressive just how much is required, We've seen players deal with dozens of foes outnumbering them 3 to one. How about heavily armored, conversion field protected, plasma gun armed robots of death with 60+ stats? Walked over. Three Killer Cans? Blasted into bits. Bloodletter? Tank? Shot to pieces. And this with characters who have just now reach 5K+ experience (something easily done after but 10 game sessions with these rules) and for most of the above had far less. I think the online game saw five players or so defeat a Chaos Marine and another time a Greater Demon (which just shouldn't be possible according to the setting).
This leads to the Psychological influences I mentioned. The amount of force needed to provide a serious threat is just too much for a GM to feel justified in using. For one thing, such opponents should be rare. And for another it just plain seems wrong to have your Guardsmen whacking hordes of foes more suited setting wise as Space Marine opponents.
In the end we're likely going to need to break through those Psychological influences and ramp up the opponents to levels that don't match the setting we thought the game was built for- just to feel that we're at risk.