I think he's referring to the fact that there wasn't a major OS update for 5 years (XP: 2001, Vista: 2006).

Every part of Vista was a significant change leading to a lot of application incompatibilities. App developers hadn't dealt with changes like that for years, so fixes were slower than they should have been.

That was a major cause of Vista's poor reputation.

"By all measures, Win9 should be a great OS. MS just has a nasty habbit of releasing experimental software as if it were ready for production."

I think they have jumped the shark with 8.x as far as their desktop OS goes.

Have you used Vista? It felt pretty much like 7 does now, to me. (YMMV etc.)