Honestly the only argument for vegetarianism and veganism that holds water in my head is that veggies have a much smaller energy footprint. Much smaller. Earth can support a lot more vegans than it can omnivores.
All these people going on about animal treatment being hte reason for being vegetarian or vegan --- let me give you some information: if you are against the way animals are treated by corporate meat packers, then fine, you are boycotting these corporate meat packers, but there is still no rationale for you not eating the deer stew that your hermit friend makes off the deer he hunts, or the free range eggs, or if you went to a third world country, the meat there.
As far as what the OP last asked, vegan cheese bears very little resemblance to real cheese. You know when some of the packages are advertising the fact that their brand "really melts!!", that it's not going to be like cheese.
I used to work in a pretty hardcore vegan grocery store, and I can tell you that as far as a healthy vegan diet goes, you are generally better off just forgetting all the old animal-product-laden foods that you used to eat. Don't try to imitate them because it will only end up not being what you expected. Instead, learn to make new food that is more suited to the ingredients you are using. Also before you make the leap, make sure you've tried some of the big stuff that vegans use - Tofu and Seitan are big in the vegan world (one of my main reasons for not trying to be vegan is that seitan and other heavy duty wheat based products makes me sick).
Personally, I eat meat and fish occasionally, and by occassionally, I mean maybe 2 or 3 servings a week. I don't believe that it is necessary to make hard rules (I'll never eat meat !!) to have an effect on the world. Just because I eat meat once in a while, doesn't mean that, by reducing my meat intake, I'm not greatly reducing the pressure I put on our planet, and also not supporting hte corporate meat packer folks. But if I'm stuck in situation where I would be miserable if I didn't go to mcDonalds (once a year), or if I'm at abaseball game and I really want to have the experience and eat a hot dog, or if my candy at the movies has gluten in it, I'm not gonna waste a great deal of energy to avoid that stuff. I think I make as much effort as a person can without letting my diet take over my life.