In 2.0 and even in 3.0 the output via firewire was synched perfectly between the program and external monitors.
You are probably one of the lucky ones that encountered that. I have NEVER had perfect sync between program monitor and external monitor over firewire. I also think that it is theoretically impossible to achieve that, due to the delay of firewire to deck, deck to monitor. It was always choosing lip sync by using sound over firewire or unsync by using the desktop speakers.
One question, what is a HUGE delay? Are we talking frames, seconds, minutes, hours or even days?
It's probably around 15-20 frames. Maybe I exagerated too much on the "Huge" part, but I use 2.0 at work and it syncs great. The program monitor and external monitor are in perfect sync. The timeline indicator is the only thing that is ofset a little in time. It is conected to a sony dsr45. I use it at home sometime with my jcv BR-DV3000 and works fine here. Before the 4.1 update it was working fine. Not only is the sync issue very annoying, but now audio must come from my deck and not my sound card.
It has never been different for me. I always had that kind of lag, even in the time of 6.0 and 6.5 and still have it today with CS4. However, and you may need to search on these fora or somebody with a better memory than I have can tune in, there have been some problems with a Microsoft DLL in the past, that made this problem worse. Now this is a long time ago, but maybe they reintroduced this problem with Vista SP2. At that moment in time the solution was to return to the previous version of that DLL. However this was way before Vista came out and only applied to XP. It may be a goose chase to find it.
I use an external monitor not for audio corrections or checks, only for video corrections, color grading, effects, transitions and the like. For audio I only use my desktop speakers, so I don't feel the need for perfect sync as much as you may. However, when I want to have perfect sync (when a client watches with me), I just use external sound and regain perfect sync, but turn the program monitor off to avoid distraction.