Re: Linux or Windows?
I use dual boot with Ubuntu 12.10 and Windows 7, admittedly I use windows mainly but I do use Ubuntu 12.10 exclusively for work. The beauty of it is that you can make it work how you want, the default desktop on Ubuntu is unity which I find an ugly mess, no problem, I use Cinnamon instead. Libre opens everything office does, though I agree with AQD that it does not always work - excel macros spring to mind as something that is a pain.
If I could be bothered to spend enough time doing it, you can use the same email profile on the same machine with Thunderbird though it takes a little manipulation. Email clients are the same however, once you have enough email in one client, it is a pain to switch it to another even in the same OS. Browsers are fine unless you use IE which you can't use on linux, but then you have Opera, Chrome, Chromium, Firefox, Safari etc so no big deal.
I do use the command line a lot at work which is probably prefer it for work, that and I'm an old *nix geek at heart