IE doesnt render HTML/CSS properly and i get annoyed I personally use Chrome. But Firefox is good as chrome as its open-source hence why its updated quicker and faster.
I personally would rather use Safari! But thats a different question....
I guess it would be a good idea, but to me it doesn't make a difference, i use firefox, but it does automatically get updated. When i got my laptop it came with ie7 and i just checked and i now have ie8, so it must update via windows update.