Very fittingly the new one is called ReCaptcha. According to what I’ve read, this one should be better than the old one, as the spambots have learned to see through (read) the letters and numbers produced by Captcha.
Not that the original Captcha weren’t reliable while I used it (can’t remember a single comment of spam getting through, while I have used it), but better be on the safe side.
One cool thing about ReCaptcha (besides being more secure), is that it actually helps transforming words from old books, that is not readable by OCR-software, into text. Thats bloody clever. So everytime you post a comment here you may be helping out “translating” an old book.
Only negative thing about the plugin is that it does not pop up when spambots register on a WP site. But the old version didn’t either, so guess I’ll have to live with it for now.