Is there value to being able to play multiple styles well?

[4_2_it]

Things I would like to see discussed include:

1) What styles should every player strive to have in his toolbox (TAG, LAG, WT, etc.)?
2) Are there levels where a certain style works best or doesn't work at all? (Please don't link to Fimbulwinter's masterpiece or the FAQ, I am looking to generate some discussion here)
3) Should your ability to play a certain style be a factor when deciding whether to move up?
4) How often do you need to shift gears (play include the level you are playing as I am interested in answers from all levels of play)?

That's enough for starters. I'm not sure where this thread will go (if anywhere). I am just looking to see how worthwhile it might for me to learn a true LAG style (I can play TAG, but prefer/slip into SLAG quite a bit)

I have my opinion (which I will share after the posters have chimed in).