On another note, I did get an interesting message from someone, claiming that training in gi is silly because you build up too much heat in doing so.
If that's the case, then I question the quality of the gi that he were using.
I have noticed, that people who buy their own gi and bring them to the dojo, tend to go to places such as the various chain sporting goods stores, and buy the cheap, 15 dollar gi that has the thickness of a few sheets of paper. These monstrosities are horribly designed, and are made of inferior materials. The fabric can't absorb any perspiration, making it stick to your skin, and then they tear apart if you do any kind of grappling work.
A good quality gi shouldn't stick to your skin with casual perspiration. The folks who bring in their own cheap gi usually end up throwing it away or donating it, and then using the gi that came with their registration package...