What was your FirstClass server / where was it? Mine was used by a large-ish (2.5k people at peak) Macintosh User Group in Canada.
It was definitely formative - I still have friends from back then, and remember logging on daily.
As you say, the transition to the real Internet and web was painful/slow for them, and obviously being a commercial software made it especially hard. The software and the user group all disappeared around the same time - hard to say which came first.
A friend of mine, Michael Pester, ran The Mouse Hole BBS in Des Moines, IA. He was running multiple lines, and I can't remember if he eventually got it up on the Internet or not - I was headed down the Internet/ISP path at the time. He was great though in letting me take a close look at all the software and how it operated. He's unfortunately passed away now, but he developed a lot of FidoNet and communications software for the Mac at the time.