During testing of Openstack Swift, I found that there isn't much GUI clients out there support Openstack Swift and the best option I could go with is Cyberduck.
Downloading it and then follow by installation on my windows test VM, everything appears to be good and smooth, except it keep saying "Login failed."
So I am pretty sure my username (account:username) and API Key (basically the password of the user) is correct however I am still not able to get in. I did some test with s3curl.pl and it is authenticating successfully without any issue.
Tried googling but there isnt article explaining this but somehow I found this article from cyberduck trac page. It looks like I have to modify some parameter on Cyberduck to allow it to work with Swift with swauth authentication module.
So as per the article suggested, I added below line to user.config and restarted Cyberduck. Now authentication seems to be working.
<setting name="cf.authentication.context" value="/auth/v1.0" />