The last machine I used that had one of those was my old Pentium 90. Other than that, I still have a ton of those disks sitting around in my closet, mainly consisting of old DOS/Windows apps. One of these days, though, I'll have to find a way to extract all that data and put it on a more reliable medium.
And those 3.5-inchers aren't *quite* dead yet. I still find them necessary seeing as my older machines cannot boot from USB devices (includes flash drives).
I still have 5... yes FIVE of those drives and HUNDREDS of those disks. I still have valuable data on them too. All the drives work perfectly. I just need to put together one of my 386/486 PC's and i can get the data off. I still have sticks of 2mb ram!!