Having never used a Fusion drive, I still think the good doctor is making a mistake. He buys Macs for a long time. (He is replacing a 2006 iMac.) These new iMacs are not going to make drive replacement easy and his decision to skip on SSD now means he'll not be using SSD for probably another six years.
We've got a Mac Power Users episode going up later tonight (or tomorrow morning) about speeding up your Mac and in it I sing the praises of SSD. I'm old enough to remember the massive speed boost we got saving to floppy disc when before we saved to cassette tape. (Yes. I saved my BASIC programs to a cassette tape.) I also remember the fantastic speed boost we got moving from floppy to hard disc. This latest improvement is no less spectacular. Having used SSD drives now for a few years, I can't imagine going back.
My advice would be to get the Fusion Drive and keep on top of things. If you are really concerned, get AppleCare and it is then Apple's problem for the next few years.
With respect to Dr. Drang's opening comments about how the thin design doesn't move him, I agree. I don't really get that as a selling point. I actually prefer my existing iMac with the integrated optical drive. Desktops and laptops are very different beasts in my book.