Stay on FW 13.37 or update to 15.31?

to answer your question about other Garmin experiences. I've owned and used Garmin watches since 2010, with 24/7 watch wearing starting with the Forerunner 935 and continuing with the 945LTE, 955, and Fenix 8. for the Forerunners (935 onward), I was a "week 1" owner and saw so many bugs. things eventually got better. I was also a beta tester for the 945LTE and 955 which was a mixed bag of getting some of the early fixes, but also living with new bugs.

in my experience things generally get better. yet, invariably, new releases brought new bugs. surprising and disappointing, but a reality I experienced for many years. for my 935, once things "locked in" to what I really wanted feature wise, I stopped updating. that served me well as I saw some people 3-4 years in experiencing dropping battery life for the later firmwares. I only owned my 945LTE for 1 year (sold it to a friend) and it finally was the "watch I wanted/bought" after 1 year. my friend sort of locked it into that mode because he doesn't even wear it 24/7 (only waking hours) and was happy with the feature set. up until selling my 955 last year, I was a beta tester and things got better and better. new bugs were introduced and reported, but for my uses, I never encountered them.

the Fenix 8, to me, is unusual in that they removed the "auto" Battery Saver feature which really is frustrating. this also is the first firmware update where I've experienced a degradation in UI performance which is another bummer.

Upgrade to 15.31 but don't use Iron Grid watch face and find another you like.

Rianor said:

I have no prior experience with Garmin—this is my first watch. I hope the update will eventually come, once everything is working properly. How was it with previous models? After each release, were there always lots of bugs at first, and eventually things got better?

I agree with what derek87wrote, eventually things get better, at least it was so with other models. And just like he said the biggest bummer was a removal of one of the core features which was a hallmark for many iterations of Garmin for conserving battery life during sleep... From what support told a lot of people were turning it accidentally and didn't know why their watch isn't syncing so instead of adding some warnings Garmin decided to remove it. So I hope that people who actually care about this feature are communicating it to Garmin(I'm doing it too) in any possible ways. So the amount of people who are not happy with lower battery life would be substantial enough to keep that feature alive. 

Rianor said:

What worries me is that so many issues have been communicated for a long time, but nothing seems to change. It feels like they’re not listening—or they just don’t care. It would really frustrate me if all my efforts end up in the trash and never reach the technical team.

So far I'm carefully optimistic and although I wish Garmin could communicate better with bug reporters, I can see that they working on bugs and some are getting resolved. 

Indeed, there are some old bugs which seems to be ignored, but I guess there must be a reason for this. 

Also, I've an impression that Solar model is kinda neglected, and the team is mainly focused on AMOLED one, and also bringing new features. I don't remember that much features added on other watches I had, it's cool, but inevitably brings more bugs, it's fine with me, and I'm happy to be beta tester and help shaping the product. But yes, I can see how people could be unhappy with watch not doing what they were promised.