A friend of mine got a new echo show eight this week and when she went to install it, it offered her Alexa +, the new AI version of Alexa. So she accepted that.
It took a few minutes before all of her other echo devices updated also, but they did.
And at that point several of her smart home devices, including a Toshiba microwave, stopped working with Alexa. These were devices that she had specifically purchased for Alexa capability, and that had been working successfully for years. 
In the case of the microwave, the echo device said (in the new Alexa + voice), ā I canāt control microwaves directly. Would you like me to set a timer?ā Which of course, was completely useless for her purposes. 
She doesnāt remember exactly which devices were affected, but there were a number of them.
After a few minutes of frustration, she ended up calling Amazon support and eventually getting escalated to an Alexa + specialist, who told her that at this time, Alexa plus has a lot of limitations with regard to smart home devices. 
Thereās no warning about this that I can find in any of the official Amazon discussions of the new AI. In fact, it uses smart home as an example of what the AI can do.
But at least as of the day of this posting, if you do get the invitation and you install it, you run the risk of losing functionality that you currently have.
The Amazon support rep was able to remove the new AI from her account, but it took about 20 minutes before it was completely gone.
So just a warning: if you install this on one echo device, it will propagate to most of the echo devices on that same Amazon account. And you may lose smart home functionality with some devices.
(She also said she lost some functionality on fire TV control of her TV, but she doesnāt remember exactly which features were affected. Just that she had to grab the button remote for some things that she previously had done by voice.)