Mainstream. It still took longer to become ubiquitous, as only a minority of homes had them in 1992, but it had passed a 25% household adoption rate, which from what I can tell, is a figure that tends to get used for judging mainstream success.

Here's an interesting set of statistics showing the rough sales of the emerging PC industry: https://web.archive.org/web/20120606052317/http://jeremyreimer.com/postman/node/329