Also, even minimal battery drain is too much, especially if it's a dozen apps all draining my battery. That can add up to significantly reduced battery life. I don't even turn on Push notifications because I don't like the battery drain, and compared to my friends using Push, my phone lasts considerably longer. I'm talking days longer. How much drain would you consider Push to be? Almost none? Yeah, if minimized apps use even half of what Push does, that's way too much to be worth it except for key apps I want to leave minimized.
Apps sitting in RAM don't take any battery at all. Even your later clarification that it does take battery because it may force other apps out of RAM to close is flawed. Without multitasking, those apps are always forced to close and re-load when you open them again. If you are able to instantly launch your most recently used apps in the state you left them, that will save battery life. It's only the apps that have been least used that will be forced to close.
Also, I'd consider Push to be a HUGE battery drain. It's convenient, but the difference with Push for two accounts on vs. off is ~12-18 hours of battery life vs. 36-48 when off. In my experience so far, multi-tasking uses nowhere near this level of power - in fact, there is no discernible difference - in general iOS4 is better at power management than its predecessor.
Since I am running a jailbroken 3gs with iOS4 it has been interesting to see the details of how Apple's multi-tasking works. Since I can easily see all of the running processes - things I would normally shut down - it 'feels' weird, and yes, I'm usually very low on RAM - but RAM is intended to be used, and as far as I can tell so far, multitasking isn't slowing anything down or harming battery life.
Listen, I understand your points regarding Apple's implementation of multi-tasking. I've been jailbreaking for years primarily to multi-task, but I think it is really important that Apple has finally released their own method. You must understand that as an Apple customer, they are not going to give you easy access to obsessively controlling things that you and I would like. In order to gain that access you need to jailbreak or move on to another platform. That's just the way it is.