If you're accustomed to leaving anonymous comments on other folks blogs, selecting "Other" for Identity, and entering your Name and URL, you'll have to change your procedure - that option is now gone. In its place, you may find (at the option of the blog owner) a selection to use OpenID comment authentication.
If you have an account for LiveJournal, WordPress, or many other blogging platforms, you'll be able to comment transparently. Without an OpenID account, you'll only be able to use "Anonymous" (again, at the option of the blog owner). And leaving a BackLink, in the URL field, is now a thing of the past.
This may make comments a bit more secure, but a lot more unfriendly. Not everybody who reads your blog will have an OpenID account. Those who don't will be unable to leave anything better than an anonymous comment, and that if you enable anonymous accounts.
Try it out - you may as well get used to it.
Click on Google - Blogger In Draft, in the sidebar to the right. This leads to http://draft.blogger.com/.
Now you're in Draft mode. See the Blogger icon at the top? So, click on Settings, for any blog that interests you.
And there are the new Comments options.