Yes, in the benchmark you will see the big difference between in the SATAII port and the SATAIII port, but in the real world usage you can't notice the differences between them, like a few seconds difference between them when you open the programs or boot up the PC. I had few SSDs in PC and laptop, as long as you start use the SSD you never go back to use the regular HDD again.
Thanks for the replies. They were about what I expected but it's nice to have confirmation.
I simplified a few things in my OP. I do have a 128GB Samsung 830 but I'm using it with a SATA I system. That's right - not even SATA II, with an AMD 3000+ single-core socket 939 CPU and DDR1. It's a stop-gap system put together from old stuff after I sold my main workhorse.
I've ordered parts for a new rig with a SATA III mobo as my main system. The one I'm discussing here is an Athlon x2 7750+ with SATA II and DDR2, which is also due for an upgrade. It will use the PII x6 1090T and start out with a conventional HDD.