I want to use these new virtual assistants.They all are interesting and seem cool to use.I have experience with all of them. They are still in their infancy, and much has improved in a lot of ways, but there are issues with each. Here's some thoughts I have on each:
Siri works great with Apple apps. It works pretty seamlessly, but still needs voice recognition improvement. It has potential if it wasn't so closed. Also if hooked into search engines more to help give answers rather than just a list of links. Also limited access to apps help more, but not allowing apps that compete with their products like Spotify, hurt it. I get the reason but at the same time it's irritating.
Google Now, which I don't fully use since I'm not on an Android phone, has a lot more use. Not sure how hooked into apps they are, but it's better used with "real talk". The cards work great, and if that could be the home page of a phone (which it might, I don't use Android phones).
Amazon Alexa works great with echo. For a voice only assistant it works great. It does use Google apps for calendar, reminders, but I wish it used apple and other companies API. It does let me use Spotify, and uses other service but I haven't dove into them yet. Alexa does with with smarthome stuff, and it's pretty sweet turning on and off lights with Alexa.
All three have their uses, and have potential, but being so siloed hurts all of them.