This took me completely by surprise: The Collins COBUILD Advanced Learner’s English Dictionary is now available from Google for free!
Of course there are better choices for English learners. Google did not include the example sentences from the COBUILD Wordbank, which means that all the other major dictionaries for advanced learners have more example sentences than the Google Dictionary — the best one in this respect (Longman Dictionary of Contemporary English) has more than twice as many examples, if you count those in the “extra examples” section.
The phonetic transcriptions have been copied from the COBUILD, so some of them are misleading. Some important phonetic information related to American English is missing. There are no audio recordings.
On the other hand, it’s hard to overlook the fact that you can now access Collins COBUILD’s friendly definitions and example sentences completely free of charge. You get reasonably good IPA transcriptions (in Unicode) that you can easily copy wherever you want. And, you avoid all the annoyances of recent software dictionaries: cluttered layout, slow scrolling, long startup time, poor mousewheel support, problems copying text to other applications. Google’s dictionary has a fast, minimalistic interface that Just Works. What more can you wish for?
It is not as comprehensive as dictionaries on DVD and its phonetics are not always trustworthy, but it is pleasant to use and has enough content to keep you busy for years. I suspect that few English learners will decide to spend money on a traditional dictionary when they can get 90% of what they need online for free. Is this the beginning of the end for dictionary publishers?