I had a machine running a Pentium D 945 ( 3.4 Ghz ) with XP MCE 2005. I bought a Gateway running an i7 920 ( 2.66 Ghz ) and running Vista Home Premium 64 bit. Both HDDs were running at 7200 RPM. Admittedly, the Hdd in the XP machine with the PD was a PATA connection and the one in the other Machine was SATA II. Both start times were nearly identical as was the load times. I then added a second Hdd to the Vista / i7 920 machine and installed Windows 7 on it. It was faster and so were load times. I then upgraded to the i7 960 and that even went better. When I intially built this rig, I moved the Hdd with Windows 7 over to it ( it was a Retail Copy so no problem ). It was running an i7 2600k. Another jump in performance. In June 2012, I changed out the GTX 560Ti for a GTX 680 and yet another kick up in performance. After that I installed an SSD. It is one of the early Samsungs ( Series 830 ). Yes, there is an up kick in performance to some degree. Took the Windows thing to 7.8 out of 7.9 ( everything is 7.9 except the processor which is 7.8 ). Bench marks went up some as well, but not to a huge degree and didn't expect it to. In June '13, I upgraded to the ASUS Z87 - Pro motherboard and i7 4770k processor. I was going from a 2nd gen CPU to a 4th gen, but wasn't sure if the performance kick would jusstify the cost. I was sure there would be some, just not how much. It was huge and worth the expense.
In short, although the SSD will make a diference in performance it is not an end all be all solution for increasing performance. It helps, but as I have pointed out in that narrative, there is a lot more involved that will result in a major uptick in performance. Even memory plays a part, although I haven't paid much attention to that aspect. As I said in my post, I am fully aware of the load times with a SSD and that it is well worth including in a build. If I can squeeze one in one someones build with in their budget I will. If I can't I will recommend that they consider getting one at some point. As for the Hex core Octa Core CPU's, they are pretty much a waste. There are few applications that are optimized to take advantage of multithreading.