It all comes down in my opinion as to what people think of as a "HUGE difference in response.".
We have two other systems in the house (excluding one laptop), all built by my good self. Mine as per sig. another has a Raptor raid array as the boot drive and another has a single WD Black drive as the boot drive. All three systems are similar in spec. with Windows 7 on them and I would have to be honest and say that in day to day usage, there is not that much difference in response / feel of the systems. Certainly not what I would class as HUGE. If I was asked which was the "fastest" then yes, I would pick the one with the SSD as the boot drive, followed by the Raptor array and finally the single WD black drive. But a HUGE difference, no... not in my opinion. Though obviously depends on what you are doing. In some tasks, obviously the faster drives shine. But overall I don't find the SSD based machine an OMG experience.
Do I regret buying an SSD? The answer would be, no. Though I stand by what I've said before on threads in this and other forums, SSD's are still not really mainstream yet. We need bigger capacities, much lower prices and decent performance that does not degrade over time.
Though one obvious application that an SSD does shines in, is in a laptop. Where drives tend to be slower than in desktop PC's (IE. 5,400 RPM and lots of "green" functions).
Only my opinion/s.