I do a Tai Chi class every week and have done for about 5 years now.
I have found it very helpful for my balance and for increasing my stamina. I am also sure it has helped my knee and shoulder problems.
The kind of Tai Chi that I do is Taoist Tai Chi , here is their website:
http://www.taoist.org.uk/
The exercises are very gentle and the instructors are very clear that nothing that you do should cause you pain of any kind. They also encourage you to rest if you feel tired. Two regular attenders at the class I go to do the exercises sitting down as they have significant back and or arthritis problems.
When I started I wanted to watch a video, but it was very much discouraged by the instructors. The 'beginners' class lasted for about 6 months. In that we learned the 110 moves of the 'set' and some basic exercises. In the 'continuing' class we practise the 'set' as well as the more 'advanced' exercises.
I thoroughly enjoy going to the classes. I have never even gone to an exercise class before, never mind kept it up, but the tranquil, non-competitive nature of Tai Chi suits me very well.
So, in answer to your question,IMHO, yes it is good for general aches and pains and yes, it is good for wellbeing.
:-))