Very nice to find a thread on Tai Chi Chuan. I found a very skilled teacher in 1995 and it was of primary focus for the next decade. TCC is very challenging. People of all ages can benefit. For the very young it teaches focus. For the very old it teaches balance and is a very low impact form of exercise with controlled levels of exertion.
The philosophical aspects and benefits are as varied as the physical. My teacher was fond of saying, "The Theory of Tai Chi Chuan is the Theory of Life." This in relation to the requirement that there be "No Excess -No Insufficiency" e.g. the physical stance is balanced, the posture neither aggressive nor retreating. The mind is balanced neither aggressor nor defender.
TCC calls for mental and physical control. You control the speed of movement through the postures, the length and width of the stance. You control your mind and guide your opponents energy away from your flowing, changing center.
At a certain level of skill it becomes a highly effective defensive martial style. One of the most intense experiences I ever had was during push hands with my teacher. He'd been chiding me regarding various positive and negative aspects of my performance. I was feeling good and "froggy" and decided to increase the intensity of our contest. He immediately sensed this change and I experienced the feeling of accelerating so rapidly that it felt as though I'd left my lower legs behind me.
It's probably the most incredible feeling I'd had in 20 or so years of studying various martial styles as well as LE defensive tactics training. I'd add that I'm a fairly stout 6'5" 255 pounds and my teacher was well past middle age and a moderately rotund 5'6'.
I wish everyone the very best in pursuing skill in TCC. I also echo the suggestion that a teacher with solid skill and experience is the best way to maximize personal gains.