If the apps are properly updated for iOS4, they hardly use any resources at all when they're in the background (apart from the app image being held in memory), unless they're specifically doing something - like Pandora playing music in the background. That's the beauty of it. You just pop 'em up again and they're back where they were when you left them. A different paradigm from on a desktop computer where you might actually want it to be doing one intensive thing while you do something else (like render an image while you email and play music or whatever).

Thanks, I may upgrade my iPhone OS this weekend !

Installed it without a hitch.. very easy.

NICE !! Love it !

If anyone is debating the issue, back up your phone and DO it.

I updated on day one to my iPod touch.
Friday updated several apps.
I ALWAYS "shut down" instead of "sleep" to conserve battery.
Monday, the battery is drained completely, no clue why.
I'll recharge tonight and check again tomorrow, but this has never happened before.

My 3G update was not an easy one. I had to do a restore to finally get the thing on. I really would not have updated but I updated an app, GPS in Motion, that was OS4 only. I wish that they would warn the user that it is not capable before updating.

This is what happened to me and what fixed it

Well, The upgrade process was flawless, took me about 40 minutes for everything, BUT, I've had it plugged in now for 20 minutes and it still hasn't registered in iTunes.
I've never had the battery drain to zero, so maybe it needs a little juice before showing up.

Sorry to hear about your problem.

Ain't modern technology wonderful?

Edit: 45 minutes later, iTunes recognize my iPod. Charging battery now.
Do not like. I hope Apple aren't over extending themselves.

My 3G’s update took AGES. As in, ~10 hours. At the end it said it couldn’t perform the update, and showed the phone’s storage meter near empty. However, I closed the error dialog and let the phone have some alone time. The contents of the phone showed up about 5 minutes later, the update HAD worked, and I have seen no further errors.

In the end, I like the folders a lot, love the built-in Wikipedia, LOVE that my in-car controls now control Pandora!! and have not noticed any slowdown.

But I have noticed CRASHES galore. I don’t think the 3G has the RAM to handle iOS 4 reliably.

Luckily I have an iPhone 4 on the way.

Also really like the rapid backup/sync. Finally! It’s as fast as I always thought it should be, and I no longer hesitate to plug in for fear of multiple-minute delays.

When you get that iPhone 4, please give us a review.

Thanks

Well, the glass scratched really badly just lifting it out of the box, and I can’t make phone calls at all when touching any part of the metal. In fact I feel a little bit of a shock when I touch it—mild but unpleasant. And I was not expecting that the retina display would actually hurt my eyes. Multitasking is great in theory—except it can only keep 2-3 apps in memory at once. Tons of crashes too.

*Wakes up in a cold sweat*

I should get it late next week. Will report on its awesomeness at that time!

Also, my 3G is no longer crashing, since I hard shut-down the device. (Hold both buttons until the logo, then KEEP holding them until shudown). Knock on wood.

P.S. Re number of apps in the app switcher at once: the one at the Apple Store had 42! I expected maybe 8!