I can second that, while it may not be the most pleasant driving experience, it is still possible to drive a vehicle after engine, power steering or computer failures. I luckily haven't had brakes fail, so I can't comment on that.
My last car kept getting problems with the computer after the dealer screwed it up while working on my car. I had to have it replaced 3 times before they finally got it right. The first failure I was doing probably 70mph on the interstate when it went. I don't think it completely failed that time, since I was able to safely drive the backroads home. I had an all electronic dash though and lost all my instruments, so thankfully there was an exit just up ahead that I used, stopped to made a call to have a ride ready to go if needed, then drove it safely home. After the first replacement, I was over halfway home and doing about 55 when everything went out. I was able to safely pull over to the side of the road and stop, the brakes were fine, but the steering sucks since you get spoiled by the lack of effort needed with power steering. After that "fix", the car died as soon as I pulled out onto the road from the dealer and I was able to safely coast it up to a break in the median, do a U-turn and leave it dead at the bottom of their driveway so they could push it back into the shop.
I also had an engine blow on the interstate while in a company van years ago and I think I probably safely made it close to a mile before stopping. I was able to safely change lanes, get to the exit ramp and get off, go across the overpass thanks to hitting the green light on the exit, turn onto a side street and pull over next to a gas station so I could call for a tow. The lane changes and turns really sucked with no power steering, but it isn't as bad when you know it is out. My dad had a belt break on an old Suburban in the middle of a right turn and he said that was quite a surprise when halfway through the turn he needed a lot more effort to turn the wheel.