On the flip side, I'm not very happy with my Nexus 7 2013 (LTE, although I never have used it). As a disclaimer I am on CM since 12.0, but even before then there were a number of issues. Tablet would stop recognizing touch or it would inconsistently recognize it; core apps would start to randomly FC; YouTube in particular has an issue where it often would say (and this continued into CM) that there was no Network and you've to press retry 3 or 4 times and then things would work. Hangouts in both regular and CM versions of Lollipop consistently has a bug where switching apps then switching back to Hangouts takes you to a random location in the conversation requiring scrolling back to the bottom frequently. This is an annoying one because there's no way to clear the screen that I've found, you can either delete the entire chat history or you can archive, but the archive is "restored" to the chat window when you begin talking to that person again.
And I apologize, after that rant I realize it doesn't really have anything to do with the topic, but I've sunk the cost already!
To be fair, my Nexus mostly does streaming video and some light emailing and surfing, these days. The display is small but high quality. Netflix keeps prompting me to sign in again, but that seems to be Netflix.
There were some hiccups with the upgrades to 5.x, but I didn't get caught by those. News reports taught me to be a bit conservative, in exercising a bit of delay before applying OS updates if there was no looming security fiasco.
Compared to my parents' contemporary and more expensive Samsung tablet, with Verizon LTE (and thus, Verizon as well as Samsung in the middle), that is still stuck on 4.4.1 or 4.4.2, the last I looked... And with some crappy third party calendar app as the default that had my mother confused for a while...
Well, via that comparison and others, I'm agreeing with the other commenter that if you can go straight Nexus, that seems to be a better way to go WRT the Android platform.
I'm hitting "tired"; otherwise, I might be able to think of some of the software concerns I've had that are not OS / updates specific.
Oh, I remember the time I added some photos to Keep, to learn that there was no way to keep them from syncing while on the cell connection as opposed to WiFi.
And, I could lament the whole "fish around on the web for random articles, for your documentation" approach, these days.
Anyway, I'm mostly responding to show a bit of support, despite our differing satisfaction levels / experiences. When something doesn't work, too often the environment/app leaves us feeling SOL. They got my money, so f--- me! ;-)
And I apologize, after that rant I realize it doesn't really have anything to do with the topic, but I've sunk the cost already!