I tried Blekko for a bit this past fall and was not terribly impressed. I, frankly, don't understand what the /slash notation is doing. is it a filter? Is it a specific type of search? However, I have been using DuckDuckGo almost exclusively for the past 2 months and I'm not sure that I'll be going back anytime soon. DDG is touted as being for the privacy conscious, but I can't say that was my primary motivation in s…
Example: I built myself a /objc slashtag that includes Apple's docs, Stackoverflow, Cocoadev.com, Mike Ash's blog, and a few other sources.
Now, when I go to blekko and search, say, "calendars /objc", I get only info about calendars in objective-c from those sources, and no noise.
Edit: I find this rather more useful than DDGs ! Syntax in that it's user-extensible, and lets me aggregate many site searches into one slashtag, rather than just punting me to a specific site's engine.