It was much more a clean-and-simple design. The less complexity and useless (to me) features an OS has - the more I like it. Of course I mean the way it works, not the way it looks.
It also took so little RAM and HDD it would altogether fit in a humble corner of my today RAM - I don't really get it why does modern software need so much more.
My views on 98 vs XP are the opposite. I ran 98 for a while on my HP Vectra VL with a ~233MHz Pentium II and, if I remember correctly, 256MB of RAM. It was dog slow, took at least 10 seconds just to open an Explorer window.
Decided to try XP on it, and I was blown away at just how much better it performed. Explorer windows opened up instantly and the whole system just ran smoother.
Not to discount this, but I do wonder how much might have been the "clean Windows install" effect. What would have happened if you did a clean install of 98?
"Clean-and-simple design." OK. So you like an OS with no meaningful memory segmentation (you could hop into kernel mode by modifying a register), awful multiprocessing support, and absolutely no defense in depth against the truckloads of malware that are all over the Internet?
It was totally enough for a personal computer. Certainly not enough for a server. I only ran trusted software and could do whatever I wanted. As for the Internet - it's a browser's job to sandbox the JavaScript.