Imma be honest here, I believe in giving companies the criticism they deserve when its due, but we've been on High Sierra on a 2011 Imac and El Capitan on a 2008 MBP, coming from 10.6.8 on both and have had no problems with the software that can't be lived with. Since upgrading to HS on the imac, external drives take a while to mount but they no longer unmount for no reason when moving data and i consider that a plus. Now, if both machines continue to work until mid-2018 when refurbished replacements can be purchased we'll feel okay upgrading. Theyve all had lots of issues over the life of ownership, expensive repairs for both, multiple times, but we dont believe in throwing things that can be fixed out. I still drive a 2001 Ford, which also has had multiple expensive repairs (including two transmission replacements! Yikes!) and still runs like new (which it kinda sorta partially is by now), so apple is not alone in having faulty components, but the software reliability has never been an issue.
Also, to anyone reading who decides to upgrade an older apple laptop that has a replacebable battery with new memory, in addition to the standard warning i like to give about buying it from a reputable company like OWC, ('Edge Tech Corp' is inexpensive, but its unreliable and definitely not a good investment. They do not honor their warranty from 3rd party vendors even though lifetime warranty is advertised and product is purchased sealed and new.), if you install new RAM and run a program like Geekbench to check the performance, keep in mind you need the leave the battery installed and not just run on the A/C adapter. The performance is throttled by apple when the battery is removed with a process called SpeedStep. It took a couple of weeks of research before i was able to pinpoint the reason for the slow performance. Hope this helps.
*UPDATE*
I retract what i said earlier in this post. Itunes is a pile. I never use it, but based on how i felt yesterday when writing the above, i decided to try and put some music on my iphone and everything went to plan. All of the music/audiobooks i had put there were there last night and this morning when i went to play something while making coffee (the absolute worst time for electronics to not work correctly), parts of the library were greyed out and said "Item not available" or something to that effect. I looked online and its apparently a common problem. The separation of audiobooks, videos and music into 3 individual apps on the phone is not efficient and it doesnt make sense from a consumer standpoint to have to switch back and forth between apps (i do realize that audiobooks can be recategorized as music, but a 'hack' shouldnt be necessary for the organization of files on a "luxury" device), maybe theres a reason from a developer standpoint why apple did this, but im not a developer and its highly irritating. Based on this, i have no idea whats going on, but i dont care anymore, ill just use other apps to listen to music. Apple is in a really sad tailspin and its very exciting to watch, because i know they're eventually going to irritate everyone enough that they wont be able to hide it behind marketing pr and theyll just crash and burn. Screw apple. Just screw those mf'ers. Ha.