Speculation on the cause is running rampant; some people blame a location-based time zone setting, others find trouble with iCloud contact syncing, still others have seen a bug involving calendar reminders in the iOS 5 notification pane. These problems aren't limited to iPhone 4S users, either — many iPhone 4 users are complaining the upgrade to iOS 5 has hurt their battery life. Recommended fixes include disabling the time-zone setting, removing calendars from Notification Center, and wiping, restoring and re-syncing contacts, among many other suggestions.

Although we found battery life of the iPhone 4S to be quite impressive — and plenty of users posting strong performance — it's hard to pinpoint an exact cause without Apple speaking up. While the company hasn't addressed this issue publicly yet, The Guardian reports that Apple engineers are actually contacting iPhone 4S users directly, asking questions about usage and collecting data to try and find a solution. Additionally, some posters in the 160-page battery complaint thread in Apple's forums have noted they were easily able to get their phones replaced at the Genius Bar. Hopefully the fact that Apple's engineers are soliciting feedback is a sign that a fix is coming.