Many users of the iPhone 3G who have upgraded to the newly released iOS4 operating system (OS) for the iPhone 4 have been complaining about slowdown and freezes on their devices during the past two months.

The Apple Support Forums have been bogged down by users complaining that since they upgraded to iOS4 their iPhone 3G’s suddenly took up to a minute to open simple applications.

As reported by reghardware, apart from the general slowdown experienced by users of the iPhone 3G, many have also discovered that the roaming switch isn’t working, frequently resulting in exorbitant bills when unsuspecting users returned home after an overseas trip.

Mobile roaming is when you use your phone to connect to an overseas network where calls are routed via that host instead of your normal home operator (Vodacom for example), at a largely increased cost. Normally users can switch off roaming somewhere in the phone’s interface, but in this case users have reported costs rising even when they disabled roaming.

Reports have also surfaced that iOS4 is draining the iPhone 3G’s battery extremely quickly and has caused at least some user’s devices to overheat or simply freeze up completely.

After a user emailed Steve Jobs over the weekend about the issue, the Apple CEO, who is known to occasionally answer emails directly replied with a somewhat terse message simply stating, “software update coming soon.”

This is the first ‘official’ word from Apple on the issue, and ‘soon’ may of course refer to anything when dealing with such a large company and such a widespread issue.