Since Chrome merged the address bar and search bar, when I type in e.g. gmail, I can hit enter and click once, or I can type in gmail.com, however while the typing and clicking may take the same period of time, the clicking is more efficient for other sites where the login isn't on the root page, or if I typo.
I think somewhat ironically Hacker News is a great example of where this pattern is a time saver. Typing in "news.ycombinator.com" is first off a mountful (typeful?) and secondly easy to typo.
As strange as this sounds, I also consider searching a "security feature." If you typo near popular sites, you'll find a lot of phishing sites with identical layouts which could be mistaken for the original sites (you did think you typed in "gmail" after all, not "mgail" or something). Search engines save you from this.