I was hired in Sept 1998 to work on the browser; we had built our own Javascript engine to add to it (since that was kinda required for the web by then). I rewrote all the table code, because it just really didn't work well when you had "too few" horizontal pixels, especially if table widths were expressed in things like %. In the end, after a major redesign of all the table code, it did better than Netscape did in the 'hard' cases.
However, before long, it became apparent with all the additions being made as part of HTML4 that sticking with Spyglass-derived code and trying to update it ourselves to compatibly implement HTML4 (or enough of it) was going to be a herculean effort for a small company (max ~350 people and briefly a $1B valuation (1999), but only around 5 or 10 people max on the browser, including the JS engine.
Given that, I made the decision in late 1999/early 2000 to switch us to the upcoming Mozilla open-source browser, and got deeply involved. The Internet-over-cable-TV part of the company failed (cable companies had other priorities, like breaking TVGuide's patent monopoly, which they paid us to do for them), and we moved onto other markets (hardware videophones) not involving browsers in 2003. I stayed involved peripherally in Mozilla, and when WorldGate dissolved in 2011 I joined Mozilla fulltime to lead the WebRTC effort.
The Spyglass internal architecture seemed at the time to be pretty reasonable compared to what I knew of the NCSA code.