What are the benefits and disadvantage of using either Git Extensions or TortoiseGit on a Windows Based OS?
Just to counter some of remarks above:
With the correct expectation, TortoiseGit provides an excellent gui for working with git on Windows. It is not a replacement for TortoiseSvn, but an improved gui over what one can achieve using gitk + git-gui (which can be considered part of core git functionality and accessible in msysgit). The only bad thing I see is how you would not need to remember all the exact commands for checkout/rebase/merge etc, since it is possible to do all that very conveniently through the gui (which is the whole point). The putty/ssh problems have more to do with the inferior support for ssh on Windows, and are not unique to TortoiseGit.