Finally, the untethered jailbreak for A5 devices (iPhone 4S and iPad 2) is out after pod2g find his dream team (iOS hacker teams, the iPhone DevTeam and Chronic Dev Team) were joining in to get this jailbreak come true. The combination team released a new tool called Absinthe.
FreakGeeks has posted a short tutorial in order to have your iDevices jailbreaked along with a video tutorial just in case it's your first time jailbreaking an iDevice.
Along with this release, new version of Cydia is also released (1.1.4) with supports for the new A5 untethered jailbreak devices.
As always, first try is not always a perfect one, so FreakGeeks has mentioned some known problem when you try to perform this actions and how to fix it. The developers has released an updated version of Absinthe to fix this problem.
My suggestion is that for few days until it has calm down a bit and then start performing your upgrade. There are too many people who have waited for this jailbreak and they will cripple the servers in no time. Just update to iOS 5.0.1 first and then you can start your upgrade process later. Be sure to make a backup of your data first, because everything can go wrong and you can't blame the developers for that kind of problems.