Is there any noticeable real-world difference between using an SATA II SSD versus an SATA III SSD? I know that SATA III offers increased throughput but is there will the average user be able to tell the difference?
To answer your question, in %99 percent daily usage, no. Say with Sata 2 you open up a program in two seconds, Sata 3 one second. I have a Apple Sata 2 Toshiba SSD in my Macbook pro, and a OWC SSD Sata 3 in the optibay and cannot tell the difference in daily usage.
If I run a speed test, yes. But most files and applications use 4k blocks random reads that take seconds to open. Most daily tasks are random reads. Reading random reads takes a second or a few seconds. The difference between the two is nil.
You can certainly tell the difference between a regular HDD and a SSD. If you look at benchmarks, you'll see that SATA III SSDs are a lot faster than SATA II SSDs. From day-to-day use, it's unlikely you will be able to tell the difference.