I used to use Google Assistant daily, and I liked it. Now I almost never do, because it is buggy, and it gets buggier with each release. It's highly accurate, *when it works at all*.
Voice recognition quality:
The voice recognition quality is stunningly accurate. It almost never gets things wrong. This is the hardest part, and they nailed it. But it seems like they had an intern write the rest of the code. Maybe it just wasn't exciting enough?
My Galaxy S5, in 2015: "Okay google" *beep* "Send a text to..."
My Galaxy S5, in 2017: "Okay google" (45 second delay) *screen flash* "Send a text to..." (15 second delay)
This isn't just my specific phone, because my wife has the same model, but with almost no apps installed, and it performs the same way.
Bad parsing code:
If you give Google assistant a command that is more that some arbitrary limit, like 256 characters or something, it gets stuck in a loop.
I say "Okay Google, send a text to Harold Smith, saying that ... 2 paragraphs of text..." Google shows me the exact correct text I spoke, in a text box, then promptly says "Who do you want to send this text to?" Confused, I respond "Harold Smith" then it correctly finds the contact, then says "What would you like the text to be?" I say the text, it transcribes it perfectly, then says "Who do you want to send this text to?"
Bad contact lookup:
I say "Okay Google, send text to Dad" then it says "I cannot find a contact named Dad." Then I open my contact list, and there is a single entry named "Dad" with a cell phone number on it. Same spelling, same case.
No retry logic:
Sometimes it tells me something like "I'm sorry, I wasn't able to contact the server, please repeat that again." Why would I have to repeat it? Didn't it just record my voice? Other times, it actually transcribes the text, then tells me it couldn't contact the server. Ummm.... what? And it does that even if the action is local and doesn't require the server, like running an app or adding an appointment to my local calendar.
Must look down at the screen to use it:
On my iPhone, it would repeat back to me the message and prompt me to confirm. With Google Assistant, I have to look down at my phone and read it. I used my iPhone to send voice texts while on the road. I can't do that with Google Assistant since the whole point is to not have to take my eyes off the road.
Poor app integration:
After I send a text, it isn't in my text history.