Google Nest Audio Smart Speaker w/ Google Assistant (various colors) Expired

Not sure if you are asking about the Nest Mini or all of the current Google Nest lineup. In general, yes, they have upgraded hardware for improved sound but they are overhaul design changes too. The original Google Home was 360° sound but it was replaced with the Google Nest Audio which is designed to be a directional speaker (may or may not matter based on each person's individual use).
At the end of the day, as someone that enjoys higher end audio equipment, the Home and Nest devices are fun and highly capable. They won't give you the depth of sound that a pair of good bookshelf speakers can but that isn't what they are designed for either. They can build a network across the entire home for wirelessly synced audio and is really well implemented.
You will not notice leaps and bounds improvement in sound between the Google Home Mini and the Nest Mini but it is better. You will notice a decent improvement in sound between the Google Home and the Nest Audio.

Personally, because I enjoy using higher end sound equipment, I view the Google devices as fun and capable more than performance devices. None of the audio upgrades really mattered to me (or are even noticed daily in use) because I don't use them for media all the time. I have Google Assistant integrated throughout the home and that aspect is fantastic. It has hiccups on occasion but compared to how we lived 10 years ago, it's all magic lol. Some people swear by the huge sound upgrades but I have every Google Home and Nest device (minus the Home Max and plus several Lenovo and JBL Google Assistant speakers) and the only big sound differences I notice are with the bigger devices and especially between brands. For daily, light use, the Home Mini to the Nest Mini was such a minimal improvement that I couldn't tell you which is which in any room in my house without looking underneath the speaker.

I use the Chromecast Audio with a dedicated amp and a pair of Monitor Audio bookshelf speakers and that is my premium audio setup outside of my home theater. Google made a huge misstep in discontinuing that device and Amazon (as far as I remember of their services lineup) did a great job of filling the void with those types of niche audio devices for all types of situations. I feel like they probably do a better job at product offerings if you don't mind being in the Alexa ecosystem. I enjoyed using Alexa for a couple of years but changed to Google Assistant about 4 years ago when there was more of a noticeable difference in virtual assistant performance and integration with my Google account. I'm sure they are both highly comparable nowadays and, as I said, Amazon has more product offerings. I just prefer the integration and investment I've gotten from Google Assistant and my smart home/Google services but if you are still pretty entry level with virtual assistant integration, it might be a good idea to do a compare and contrast between the two offerings to see if one might fit your needs better than the other.

Lastly, before the inevitable comments begin about how someone doesn't want this product because it, "spies" on them, please also include with that comment what smartphone or other connected smart device you are posting your comment from. I have yet to have someone give me an example of a smart device that lets them comment on Slickdeals that doesn't have a microphone, camera, or internet capabilities and I'm really looking forward to investing in that kind of tech

Sam's Club has a two-pack for $88.88 https://www.samsclub.com/p/google..._product_1

Normally Costco is in sync, but looks like they're asleep on this one.

I was more concerned about the voice assistant response. I feel like that has gotten worse.