Git and Mercurial

I would like to know:

• What's the difference between Git and Mercurial?
• What are the pros and cons of using them?
• How good is the Windows support for both tools?

Some time back google did an analysis of Git and Mercurial. You can read it online on

http://code.google.com/p/support/wiki/DVCSAnalysis

(according to a comment this may be related to the above dead link; since comments are volatile, I am editing it into the answer)

You may want to read this question on stackoverflow:

What are the relative strengths and weaknesses of Git, Mercurial, and Bazaar?

Git and Mercurial have more in common than they differ. Both are excellent.

I use Mercurial and have no experience with Git. From friends that use Git I hear that it takes some getting used to, but after that it's awesome.

Windows support... I believe there are GUI front ends for both. Mercurial is written in Python, so no problems there.

Here's an article about distributed SCMs by Eric Sink:

Mercurial, Subversion, and Wesley Snipes