Comfort
The headset is quite heavy, 555g without the cables. Most of the weight is at the front and you can definitely feel it when you swing you face from side to side fairly fast as you dodge virtual swords, fists or bullets. The attached straps are fairly elastic too so this doesn't help as they do stretch to some degree. Consequently you want to tighten it quite a bit. The down side for doing this, as a glasses wearer myself, is that the frame legs of my glasses can dig into the side of my head. The foam facial unsert does have a cut out at these points and they are easily made deeper by using some scissors.
Once you are immersed in a game you soon forget the weight and even after an hour of play the Vive remains comfortable, with no fogging or even nech ache.
The only downside is that if you are playing a vigourous gamea and/or your room is warm the sweat from your face gets absorbed by the foam face insert.
Fortunately you can by a 3rd party cover to protect the foam from a company called VRcover. These are available in both cloth and a waterproof vinyl. I will be doing a review on the waterproof one.
Safety
The big problem with VR is that you cannot see what is around you and if your headphones are good you cannot hear what is around you either. You become so immersed in what you are doing that you become totally oblivious to your surroundings. Steam VR has a "tap tap" function whereby if someone ones to get your attention they press the F1 key and you hear a noise through your headphones. I could not get this to work so my wife resorts to slapping me which is rather unsettling !
Steam wisely incorporates their chaperone system which forms a wall around the periphery of your play area. The colour of this wall can be changed as well as how bright it is. Since this does break the immersion you can turn it off but you do so knowing that you might walk into a wall..
In addition to the chaperone system you can activate "Tron" mode. This uses the camera feed on the front of the headset showing you an outline of the room around you. Pressing the system button brings you a live feed from the camera on a postcard sized screen that pops up from one of your controllers.
The cable from the headset is long. It must stretch about 15 ft, including the cables from the breakout box. It is also quite heavy and thick. Over time it starts to get twisted and thus shorter. This is when it is prone to get pulled out of the PC or breakout box which causes an abrupt loss of the game and requires you to restart Steam VR. Also, the cable can start getting in the way of your legs and although I have not tripped over it I have trodden on the cable many times which yanks your nhead backwards.
Unfortunately, given the technology we have today, we need the cable to maintain low latency but ultimately a wireless solution would be ideal.
I will be looking at various methods to reduce this cable issue.