Ok here goes.
1) I don't get flies and grit in my eyes because I ride with glasses on at all times. In the day I wear shades and in poor visibility / at night I wear 'yellows' like
these. The yellows have a strange effect of massively reducing glare from oncoming traffic whilst actually enhancing white road markings. A good pair of well-fitting glasses offers as much protection from the wind as a full-face.
I find that even on the coldest day, glasses are far less likely to steam up than a fullface with a visor because you're not breathing into the same airspace, and even when they do mist up, they clear much faster.
2) I know that I have no chin protection. However, I am MUCH less likely to suffer neck injuries as a result of not having a chin guard. Its one risk paid off against another and its the choice I made when I started riding in an open face.
3) You will never understand riding without mirrors until you do it. You have MUCH better rearward vision by turning your head than by using mirrors because your body doesn't get in the way and once you get used to it its as natural as looking in a mirror (R1nut - you can actually see directly behind you so yes, you do get 360 deg vision). You also learn to ride much more defensively IMO without mirrors. I don't think its reasonable to assume that you need mirrors to be properly aware of your surroundings.
Its the same thing as riding without indicators (my 1st proper bike never had and never will have indicators). You learn to position yourself on the road properly and plan ahead much more, and an arm stuck out makes the point much better than a little blinking amber light. Yes there are certain circumstances where you have to take extra care, but you soon learn to adapt.
At the end of the day its about personal choice. Touch wood I've never had a spill on the road and I've never been hurt whilst on any bike. I ride within my abilities and the limits of the bike and road which is alot more than can be said for the plastic rocket bregade, who ride 3 days a year when the sun's out. I don't often have problems with ROWV which I believe to be down to a combination of the appearance of me and the bike and the exhaust noise. However, I refuse to accept that I am more of a danger to myself and others by choosing a particular style of helmet and no mirrors. Don't knock it until you've tried it.