DDG is the fastest of all the privacy-respecting engines, but it consistently gives me the least accurate results. It works if you search for mainstream keywords, otherwise it mostly doesn't.

Google's strength lies in (and always has been in) the tail and ambiguous queries. Everyone can get the query "facebook" right; try the query "how to disassemble tile" on Google[1] and Yahoo[2] or Bing[3]. Google knows the difference between "tile" (the gadget) and "tiles".

[1] https://www.google.com/#safe=off&q=how+to+disassemble+tile

[2] https://search.yahoo.com/search?p=how+to+disassemble+tile&fr...

[3] http://www.bing.com/search?q=how+to+disassemble+tile

Interesting example. The results for ddg improve dramatically if you add "tracker" ("tile tracker"). I'm not sure I'd consider Google's default results better -- but then I don't own a "Tile". I do get that inferring that the connection "disasemble tile" implies something other than ceramic tiles (as opposed to "repair tile" -- here ddg and google are very similar for "repair tile" and "repair tile tracker" -- although none seem to give a result for software/a device to track progress of repairing ceramic tiles...).

I use it for all manner of searches. Knowing how to tune a search appropriately helps. Tossing in an additional keyword, or a set of associations can help:

    (phrase one| phrase two|phrase three) 

Using bang syntax is also quite useful.

In my experience, where a DDG search doesn't turn up good results, an SP or Google search (both bang-searchable) are generally not much better. I'll revise my terms at that point.

Again, date-range is the notable exception, and it's not a minor issue.

The main feature I'm missing from DDG is the ability to filter results by date. I end up going to google often without it.