I bought my Echo Dot a few months ago and love it! It is true to say that I have never tried the Google assist so cannot compare between the two but I have used the Google assist on my mobile and find the Echo Dot beats that hands down. Set up is easy but as far as i am aware needs to be done via a mobile phone, tablet or kindle device. Apart from general everyday tasks like weather forecast, news updates i use mine as a timer and for any quick general knowledge questions that you would usually have to pick up a mobile device and ‘Google’.
There is a vast array of tasks that can be activated via the app, i have only tried a few and fail to keep using as you have to access the specific task via a certain voice commands which i find hard to remember for each specific task. Recently, I have purchased wi-fi light bulbs which are amazing and again pleased with how easy they were to install and connect to my Echo Dot. These allow me to turn on all my lamps and lights via voice commands. I would definitely recommend the Echo Dot and look forward to connecting more devices to it as and when they are released.