I was the guild leader of a pre-release guild in AoC which waited for 6 months for it to be released, and I was in another pre-release AoC guild for 4 months previous to that; I only experienced two release date setbacks in total, but there were heaps previous to those. The players waiting for AoC were starting to get very pissed off at waiting by the time it was released.
A few months after release, and as lots of players were starting to hit 80, you know what they were saying? They wished Funcom had spent more work on the game before releasing it; it was "unfinished"; they wished there was more content at certain level ranges.
What happened? 6 months after the game had been released, the playerbase had shrunk dramatically. Many guilds had quit together, including mine by then.
Of course, many of the issues are 'fixed'
now, it seems.
But if there's one thing I learnt from that waiting? Don't rush Funcom. Chill out and enjoy the game like you've been enjoying it for years previous. It won't kill you.
A finished, unrushed engine is better than an unfinished, buggy, incompatible engine which has been rushed through development.
The very same people screaming for the engine to be ready will be the same people crying that it's buggy and slow if it was released sooner rather than later