This is more of a concern than an actual disadvantage, but I have a concern regarding Google Pixel is nothing related to the hardware, but I have some high degree of uncertainty about Google's long-term commitment to releasing future Google Pixel phones to follow the first iteration devices. Google is known for closing down services that don't reach a high number of users, and we are talking about in the tens or even hundreds of millions, depends on the type of service or product of course. I can understand the business decision of it, but Pixel is a new device, and it might not get a good start in the first years and the phone might need another iteration or two before it reaches its full maturity and until people will start ditching their iPhones or other Androids in its favor.
It would be amazing to see a Google branded phone staying with us for the long term and giving a strong competition to the iPhone. Google has a lot to add to the mobile market when it comes to software. I think that Google Assistant is just one, but excellent example what Google can achieve with its experience as a software company and its investment in AI technologies.
I think that Google will stay for the long run because it serves as a foundation for Google to develop its software-based technologies without relying on third-party manufacturers (although HTC assembles the Google Pixel and Pixel XL phones). This works the same as in Daydream, it's VR platform. Google knows that there is at least two device that is fully compatible with its current and future technologies planning.
As you can see, I am kind of split with my thoughts about this subject, and I just hope that Pixel brand will be adopted by many users so Google can continue not just support it, but also expand the Pixel lineup with even smarter AI and other cool features - and we know Google can do it extremely well.
I think that many users will wait to see if Google is committed to the device and then decide if it's the right time to switch. I might takes quite some time, and I think Google need to hang on, even when sales won't be strong as they expected. As for now, things look pretty good and due to a huge demand, the are major delays across the world. So Google got to a good start, and we just need to hope that indeed the future iterations of these phones will be even more amazing.