Making tea is an intricate a process as you want it to be. The different ways all provide different tastes and different convenience/taste
Personally I make 95% of my tea the way fondue suggests above - that is: teabag in mug, boiling water on bag, swoosh about etc. Adding milk last. The main reason for this is because I am lazy.
Tea (we are talking plain old PG Tips and Tetley here) does taste better made in the pot - but who is going to bother with that unless they are making more than about three cups of tea? Equally, I think tea tastes better with the milk added first, but this can't really be done without using a pot, unless you want to pour scalding water into milk with a tea bag in it, and that would just be freaky.
About the only concession to taste over convenience I make is not re-boiling old water - and when you see the inside of my kettle, you'll know why. It does taste better too though of course.
Another point no-one has touched on, is What type of milk should you use? - Semi-skimmed, Full Fat, even (gasp)Skimmed? Hmm. I just go with whatever is available though it does make quite a difference.
I enjoy other teas occasionally, but the English cuppa will always be teabag based. To me, drinking Darjeeling or Earl Grey - both of which are very nice, is a totally different experience to making tea, say, to have with some digestives.
I also have no problem with how other people drink their tea, if they want to spend the time and money, but we do all know that...
it is rather a faux pas to add milk to Earl Grey.
Oh yeah, I nearly forgot - blackcurrant fruit tea is uber-nice and tastes like hot Ribena and tea all mixed into one. Yum!.