I had a similar experience. I forget the exact timing, but it was probably around 2002 - 2003 that Linux felt "good enough." I was at a startup that finally considered putting its "enterprise" stack on Linux.

At my employer in 1999 we were maintaining home-grown binary modification to the Solaris kernel so that TCP segment send and receive were not O(N^2) where N was the number of addresses on the interface :-/ It was, as far as I could tell, an operating system that nobody had ever tried to use before. For anything where we could avoid Sun we used FreeBSD. One of the nice things about the free Unixes of that time was that process and thread creation or destruction were orders of magnitude faster than on Sun. To me, Sun was obviously in a lower category than Linux/FreeBSD/NetBSD.

Yep. Solaris was the Unix for the 90's. I worked at a couple of early ISPs and users demanded Sun Solaris shell servers. At a couple of startups, we built everything on Solaris because Linux wasn't accepted in the enterprise yet.

By the early 2000's, 1) Linux was solid, why bother with Solaris? 2) ebay and other channels were flooded with used Sun hardware from failed dot-com companies anyway. No need to buy new.

I was asked to benchmark some Solaris/SPARC vs Linux/Intel hardware in around 1997, and the price-performance of the Linux gear was easily 3+ times better. There wasn't really any comparison, especially when you consider how you could buy white box PCs from a local shop, grab a Red Hat ISO for nothing, and have an installed Linux server in 24 hours, compared to weeks to get something more expensive and worse for the Sun option. Even if Sun had been more reliable, it wouldn't have mattered because you could buy 3x the PCs and keep two in a cupboard, or more likely just replace everything with more numerous and better performing Linux PCs which was what we did.