heh, I had ot for a month or so on my Pentium... then the integrated graphics chip failed and I couldn't see anything on the screen. I learned what a heatsink was then, so it wasn't all bad.
Win98, is essentially win95 with all sorts of stuff preinstalled, but it also adds some system-level stuff like FAT32 (also supported by 95 OSR2) as well as USB support (much better with 98SE, absolutely none in 95 retail, and most vendors didn't support the implementation provided by OSR2).
Windows 95 was the first release of windows that had a "taskbar; all previous versions used program manager- including NT 3.51. NT 4 took the taskbar and used it for itself, as well.
It was a rather messy time to be programming windows- a lot more variables then there are now. In order to have coolbar/rebar controls, you'd have to either be running windows 98 or later, or running windows 95, and then check (i nthe win95 case) that Internet Explorer 4 or later is installed- and of course you need to change the functions you call if you discover your running on NT. Even big software companies couldn't get the version checks right.
Now all the "API" changes are really isolated to .NET, which is really more of a separate platform then the win32 API, too.