I remember my sister got an S5 when they came out and cracked the screen within a couple of weeks. She had dropped it onto her car seat, it bounced and hit the plastic armrest. It was inside the slim folding case they came bundled with at the time. Might be anecdotal and nitpicky, but for a device that expensive to break with such little force was disappointing to say the least. I think it was a combo of poor reinforcement of the front glass due to its design + older gen Gorilla Glass (as well as somewhat careless use of course).

To flash a custom rom, IIRC you had to unlock the bootloader and even after relocking, Knox wouldn't work so the warranty would be void. And without VoLTE or current Android support, it'd be barely usable today. On the whole, it only really stands out in the context of later Galaxy S devices not having user-replaceable batteries. Samsung still sucked at the time, just less so in that particular area.

The only really good Galaxy S device for its time was the S2. Snappiest Android experience from any vendor & it wasn't even close. S3 was where they started coasting downhill.