especially as I have never seen software responsible for breaking physical hardware.
Does happen occasionally, less so now (unless on purpose to ruin devices the manufacturer deems inappropriate).
I'm sure you're old enough to remember early vga monitors could be tuned to channel smoke if wrong video card driver was used 
You saucy fooker

I should have rephrased that slightly better.
Yes it is still possible for software to break hardware (I can rewrite a kernel now to drive the CPU potty in a phone and kill the battery in an hour), but it would have to be an intentional act to do it.
PS
Yes I do remember those days
Speaking of Lolipop I believe it's available for the S5 now although not OTA yet (wasn't last I checked anyway) but is available using Samsungs software Kies 3, Is it worth updating now or is it best to wait a few months ?
I'd personally wait a short while for others to test the ROM first.
I don't know about v3, but the previous 2 incarnations of Kies have been abysmal TBH (a bit like installing the old AOL software on your PC, once you've done it the PC is fubared if you want another piece of software to work afterwards).
The official upgrade will be available to those first who have a genuine SIM free phone, those who got it from the likes of O2, Voda, etc will have to wait for their service provider to "norse" it up before it is released to them.