The Invoke is an amazing speaker. I bought mine in the 5th Avenue MS Store and was flabbergasted that the music that was filling the ground and mezzanine floors was from a single Invoke - at about 30-40% volume.
The sound is amazingly clear, crisp and with a nice deep bass.
Would we recommend the Invoke? That would be a qualified 'Yes'.
The "Harman Kardon Invoke voice-activated speaker with Cortana by Microsoft", to give it it's full title, is a wonderful speaker and a great audio addition to any room. The design is made for the device to become invisible and blend into almost any environment - you don't want to see the speaker, you want to hear it. The Invoke fulfils that brief excellently well, the sound does the talking for this device.
As a Smart Speaker, the Invoke has some advantages over its competitors - the sound is crisper, louder and deeper than an Echo; the integration with Cortana on your other devices makes it easy to integrate into your life; the precise local knowledge in some aspects is better than Alexa, but the Echo and Google Home devices can be better for finding audio content.
Microsoft is updating Cortana at a frequent pace, adding skills and functions that were not there at launch for the Invoke, so it is possible that it can catch up on functionality available elsewhere.
Actually for Black Friday, Microsoft were offering this device for $99, as opposed to $199. At that price we would change this from a 'qualified yes' to a definite yes. As a quality Bluetooth speaker it would not be rivalled at that price - the Cortana part is a bonus on top of that (and if that Microsoft / Amazon AI partnership ever actually comes about, then you'll have Alexa on the device as well).