From personal experience living in the Forest of Dean with wild boar on our patch, they are indeed extremely shy and keep themselves to themselves.
I regularly camp with the children up in the woods and we listen for them rooting around, but they never approach the camp - presumably due to the smell of fire and us.
Similarly often startle one nipping down the track to or from the village pub and they are off like a shot.
There is no reason to be overly scared of them, although you clearly dont want to corner one as they will try to survive and if that means running through you, I am sure they will.
Going by the size and speed of them, I know I would be coming off second best in that scenario - even if I am fit and 6'6".
I tend to shuffle the stones on the track as I walk to make a noise so as not to startle them - the suffling has nothing what-so-ever to do with my neighbours excellent cider mind!!
On occasion when I have spotted them before they spotted me, and presumably the wind was in the right direction I have observed them from within 10m as they go about their business in the undergrowth completely unaware of my presence.
They can be a bit destructive with the verges down the track and once the garden is established will have to fence them out, but quite like the fact they are around and they are just doing what they need to to survive.
Mind you, one or two have ended up in a neighbours freezer over the last few years when they have got carried away in his fields, but in the absence of any predators a little culling can be a good thing.
We have video of a sow with 14 half grown piglets in the garden from a few years ago and have purchased a maplin camera as recommended on here to get some more footage.