Feb 2, 2017 update: improvements have been made!
The other day I saw a headline about a new extension for the Chrome browser from the Internet Archive, Wayback Machine. I had initially ignored this, assuming it was the same thing as Wayback Chrome, but upon further inspection, the latter, which has been around for quite some time, is from a third-party, not the IA itself. That said, I'm keeping them both installed, and here's why.
Wayback Chrome, the earlier extension, has always worked upon a mouse click. You land on a page, see that it doesn't resolve, and then click the Wayback button, which takes you directly to the archived version at the Internet Archive. I just tried it for http://change.gov which initially lands me at:

I then hit the wayback button in my toolbar and am taken to the archived website.
This newer extension tries to be more helpful in the following way (emphases mine):
By using the “Wayback Machine” extension for Chrome, users are automatically offered the opportunity to view archived pages whenever any one of several error conditions, including code 404, or “page not found,” are encountered. If those codes are detected, the Wayback Machine extension silently queries the Wayback Machine, in real-time, to see if an archived version is available. If one is available, a notice is displayed via Chrome, offering the user the option to see the archived page.
That means it doesn't work at all for my previous example, because http://change.gov doesn't return a 404 error code, it returns a, um, I can't figure out what code it's returning :-(
I also can't find a single page where it DOES work, because I can't think of how to find a disappeared page and I've already spent 20 minutes trying to find an example. Hey Archive.org, can you put an example on your blog post please? OK, I kept looking and finally found an example for you: http://www.supremecourt.ohio.gov/publications/annrep/IOCS/2011OCS.pdf Hit that with the new extension installed and you'll be offered a visit to the archived version. Which OMG doesn't work!!!!!!

FFS. I guess I'll keep it installed for those times it might pop up and actually prove handy, but I'm going to continue to rely upon the original Wayback Chrome extension I've been using.
YMMV.
Oh, I looked again at my post title. Maybe it doesn't suck, but it's sure not as useful as it might be! Much too restrictive in the error codes it acts upon IMHO.
Update on Jan 17, 2017: I've been emailing back and forth with the Director of the Wayback Machine and have agreed that the word "sucks" is too strong, so have changed that out from the title of the blog post :-) He gave me a URL to test with, http://www.pfaw.org/attacks.htm and mentioned that URL does appear on the Chrome web store, and it has also been added to the original blog post announcing the tool. Finally, he clarified that "http://change.gov results in a DNS error. The "Wayback Machine" extension does not detect DNS errors at this time. We are looking into adding that feature. Note that we ARE detecting error conditions: 404, 408, 410, 451, 500, 502, 503, 504, 509, 520, 521, 523, 524, 525, and 526 We are also looking to add a persistent UI to save and lookup URLs on demand."