It was definitely just a feeling.
I wouldn't know where to begin for running any tests to back this up.
I turn my computer every night so each time I reboot the cache is wiped from RAM. Unless there is something I'm missing about RAM.
So the first time I open Iron (on a startup) it usually takes longer than I would prefer to load up. I feel like it did not when I had Chrome using RAMdisk; and facebook certainly seemed a good deal faster.
It's entirely possible that my new setup (hardware and Win7) and switching from IE to Chrome made the difference; but Chrome definitely felt faster after I added RAMdisk to the equation.
In the end though it can't hurt. Boot time takes a little bit longer when it loads the image into the RAM, and when it saves it when shutting down. I usually turn my computer on then walk away and do other things while it boots; and I couldn't care less about shutdown time; unless I was doing something that required constant restarts like when I was overclocking.