I heard a lot of hype about SSD's and in the end I got one. But I never noticed any speed difference between my HD and the SSD.
Desktop HD's with 7200rpms and 11ms access times are plently fast for most systems
May be true on some systems. I recently refurbished an E3300 (C2D dual-core 2.5Ghz) rig, that had a 500GB WD HDD that was new in 2011. Not a really slow drive, fairly speedy.
Well, I upgraded it to Win10, and added an SSD. I had to use a SATA6G PCI-E 2.0 x1 controller card (also for the AHCI support) to add a SATA port. The slot was only PCI-E 1.0, so it was limited to 250MB/sec bandwidth (both directions). The SSD doesn't seem to have quite the random-access "snap" that my other rigs that use an SSD have, when using a native chipset controller. In fact, it seemed to me that opening programs with the SSD, might have been slightly more laggy than the HDD was.
But things like Malwarebytes scans really benefit from the SSD. You can see that they are like 5x faster with an SSD. That's what really got me into SSDs in a big way, when I was actually able to quantify the performance increase like that.
I noticed something else. Having been used to a HDD's limitations, I would unconsciously limit my multi-tasking, as to not bog down the HDD.
Having a decent SSD installed into the system, you don't have to really worry about that anymore. You can burn a DVD, while copying ISOs over your LAN, and listen to streaming internet media, and web browse, all at the same time, without worrying about buffer underruns.