There is no myth.....
[FONT=Arial, Helvetica, sans-serif]Depends on the wiglets and how often they update. Stuff like one for music that isn't being used wont take up to much battery but something like system info that updates every 30 seconds-1 min will...[/FONT]
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I believe it is a myth based on fear. Truth is, everything uses battery power to some extent right? We pick and choose what we do with our phones to try to get the best battery life possible. A widget that updates every 15-30 minutes, or when you have your phone in use shouldn't cause more drain than a background push notification, and those are going off all the time on peoples phones. If someone wants to use a system info widget that's constantly updating that's up to them. I have 5 widgets on my iPhone now and I'm seeing the best battery life I've ever had. For all I know iWidgets was made by some kid in his spare time, certainly Apple could give us widgets that didn't cause any noticeable battery drain as well!? Every new feature I can think of Apple has added over the years has been optional, you can go into settings and turn off the notification center, and use those horrid old pop-ups if one wishes. so I at least wish they would give us the option so that those of us that want them can use them. People get so hung up on their dislike/hatred for Android that they seem to want Apple to keep limiting the functionality of the iPhone so that it doesn't dare mimic any of Android's features, truth is Android phones have some really useful stuff, and many of us would like to see them added to the iPhone so that they have that Apple polish.
But anyway, I doubt we'll ever see them, it looks like all we are getting next week is some re-skinned icons, no real new functionality which the iPhone needs.. Hope they've kept the good stuff under wraps!