Boot time is overrated, I am always concerned with program opening times. The difference between my ancient XP and newer 7 (with more RAM etc.) is/was mixed. There are still programs that take their time opening up, others which are definitely better.
Which is why I mentioned that Office 2010 programs open near instantly... However, that was in the context of SSD vs a traditional platter based HD, not XP/7/8. My memory of going from Vista to 7 to 8 on the same hardware (the XP to Vista jump was one not only of a new OS but also a significant and complete upgrade in hardware) is a bit hazy, but I *think* is more or less in line with what you're saying. Regarding boot times, I used to be of the same mind about them not being so important because I rarely restarted my computer. However, now that my computer boots as fast as it used to awake from sleep, I'm appreciating the decreased boot time a lot and find that I shut it down rather than putting it to sleep at night. Not a huge deal, I suppose, but a noticeable one for me!
ADDED IN EDIT: I should install Corel Paint Shop Pro to see how quickly IT loads under Windows 8 on an SSD. It was still a pig on a regular HD - anywhere from 10 to 25 seconds to load.