Recs.
Updated
DuckDuckGo is a competing search engine to Google that focuses on increasing search productivity while protecting user privacy.
SpecsUpdate
Pros
Pro Very protective of user privacy
DuckDuckGo does not collect or share any personal information. Their privacy page has a great rundown on why privacy is important. The most important repercussion of this is that DDG doesn't use the data collected to tailor results, avoiding exposure to the "Filter Bubble".
Cons
Con Owner would compromise his service/customer privacy
In a question to Weinberg, “if you were served an NSL or were commanded to compromise your service/customer privacy in any way, would you and could you just pull the plug like Lavabit did or would you run into opposition from shareholders/investors that would prevent you from doing so?” Gabriel Weinberg said: “No one is preventing me from doing that.”
Con Search results are often unrelated and limited
Common conversions do not work, i.e. searching for 15F to C does not give you the conversion but just a bunch of conversion websites. Very frustrating. It's a simple thing but makes a huge difference to the browsing/searching experience. Also location based only works for the country you're in. Searching for, say, McDonalds only gives country results for McDonalds and no local results such as where a local restaurant may be. Not very helpful.
Con Bangs do not protect user privacy and can be misleading
Using these bangs will instantly connect you to the service you requested. For example typing “!g white cat with green eyes” and hitting return, drops you off on the Google website to display your results (thus logging your IP, search term and browser info immediately). It does not get you Google results inside DuckDuckGo. It is reasonable for DDG users to assume and expect a private search engine warns if there is a risk to that privacy being lost, like it does with Youtube videos but in the case of Bangs this does not happen.
Con Form over function (overall search experience is poor)
It's nice to adjust the settings and all but after a couple of days you will want to go back to a more functional search engine.
Sure DDG looks shiny and !bangs are great but many wouldn't consider it as a viable alternative. Better results for search queries is more important than fancy looking CSS.