Over the last year, I've made heavy use of Drum Replacer, Vocal Alignment, and I've used the new Aux track functionality on every mix since it's been available. I'm also glad of bug fixes and refinement, but in terms of actually getting my job done, those three things, and a handful of others have been definitely more valuable than any bug fix I can recall in the same period.
I think if Sonar went for a feature freeze, that would give some other DAW the opportunity to significantly pull ahead. And while I'm fond of the company and all, I'd switch if something else had a stronger feature set. I'd also switch if bugs were so egregious they got in the way. I think they've got the balance more or less right.