Wow. HUGE topic, of which I am by no means qualified to answer, but I'll give it a basic shot.
Off the top, you are still transitioning from the previous regime, and the previous regimes personel. I think you underestimate this issue. Saban came here, with a lot of successful baggage, and the majority of your fanbase equated that with instant success. By instant, I mean within 2 or 3 years.
That's a lot to assume and saddle him with. This is not college. You simply can't recruit your personel. And the ones you can (free agency), you're still limited via the salary cap. I think the cap has been overlooked in your total success. If Saban had his way and was able to replace a lot of the old guard with the new guard he would, but alas the NFL in the post-salary cap era is much different than pre-cap. You have to build carefully.
You have also changed a lot of coaches (OC & DC.) I know that you have replaced them with quality individuals, but I would assume that takes time. It is hard in today's NFL to have consistancy, but the more a group plays together, the better they become as a team. It has hurt my Patriots more than some would care to acknowledge.
You guys (please don't flame me!) have also vastly overrated your players. Before this season, the majority (not all) said how good your team was, how they would take the AFC East from the Patriots for sure, and that many of your players (ie. Ronnie Brown, Zach, Taylor, etc.) were the best at their positions. I was even hearing how amazing Traylor was. Hey, they're your team and you are entitled to that opinion, but realistically they are not. Doesn't mean they are not immensly talented though. The point is that your pre-season '06 hype put false expectations on your season. And for the record, there are not many Pats players I would say are the best either.
As for your now infamous "O-Line", they are not nearly as bad as being blamed. Funny how much less pressure is on the QB position with Harrington back there. Culpepper sold a bag of goods that seemed false (as many opposing fans said before he played) about his injury status. It didn't help you fans that reports out of camp said he was "ready to go" and "looks great!".
Part of it is just bad play. Some of your position players need to step up and play better. It is a fine line between winning and losing in the NFL. I too thought you guys would be far better than you are currently playing, and part of me still believes you will start to turn it around this season.
I am not one for trash talking or running my mouth off with smack. I give the Jets a ton of credit for playing far better than I ever thought they would. I also think Buffalo is underacheiving too, I thought they would play better. As for my Pats, well, I think they are overperforming right now and thought they would have been a bit worse so far.
To sum it up, you guys have been so good for so long that I think the modern NFL is forcing you as a fanbase to rethink your team. You can't simply be Super Bowl bound or instantly turned around because you got a talented coach, RB and QB. It takes far more to create a champion, including at times, luck. There have been many talented team in the past who never won the Super Bowl either.
I would end with this. Even though you are not doing well, there are plenty of positives to build on, even if that means next season. You could have Herm Edwards or Mike Tice as your coach, more style than substance.
Now... flame on!