I can not figure out why this is always such a debate. BMW paid a lot of guys with PHD after their name to come up with a spec for what we should use. I am pretty sure these guys did not pull it out of their ass, and they don't work for free. So why does everyone feel the need to second guess them so much? Unless you also have a PHD after your name, and know something that they did not, it seems like a waste of time and effort to try to prove them wrong. It is so damn simple to just use the oil, coolant, and gas that BMW reccomends, and not have to worry that you may be wrong. It is not as if you are really saving any significant money by not following their advice. If they made it difficult to find, or significantly more expensive to use what they reccomend, then it may be worth a second look. But some of you are actually paying more to use something they don't reccomend.
To me, it seems like a simple thing to do. Use what they tell you to use. They are not profiting from their reccomendations. If they wanted to do that, they would not let any other company know the specific additives that make up the BMW LL-01 spec, and they would be the only vendor for it, and they would charge a fortune. If that was the case, I would be researching the spec, and looking for something close. But that is not the case, so why all of the 2nd guessing the experts? It is simple. Use what they say to use, and scratch that off your list of things to worry about.
But, use what you want. You may be fine, you may not. You may not own the car if/when the problems show up. I plan on keeping mine, so I see no need to second guess them. In fact, I suggest all of you use the cheapest, non-synthetic, convienence store crap you can find. You will keep the parts vendors in business, so when I need a part, I can still find it at a decent price. And if you choose not to repair it, then that is one less e46 on the road, which will make mine even more valuable! You know, that 75W-90 oil they use in the transmission lasts like 60k miles. Switch to that in your engine, and you won't have to change your oil for years!