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.
Vista had some really good ideas, executed poorly. Win8 has some good ideas, executed poorly.
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.