With the release of redsn0w for iPhone OS 4, beta4, I thought it might be worth it to fill you in on what’s working with Cydia and iPhone OS 4. The short answer is: Nothing, really. As the iPhone Dev Team has said, this jailbreak is just for developers to work on their jailbreak apps, so they are ready when iPhone OS 4 is officially launched, and the next jailbreak tools are released. Another important thing to remember is, iPhone OS 4 includes a baseband update, so you will not be able to unlock your iPhone, if you update to OS 4.

So, what IS working? OpenSSH is fully functional, allowing you to explore the root file system, from your FTP client. This has allowed for a few cool tweaks to the iPhone 3G, on OS 4. By adding a couple of things to a plist file, you can enable multitasking and homescreen walpapers on your iPhone 3G. Something that will not be available in the official launch.

As for themes in OS 4, Winterboard is not working yet. MakeitMine is working fine, so you can change you carrier and banner text. With homescreen wallpaper enabled, you have some customization, but anything else you want to change, has to be done manually, via OpenSSH. If you’re going to mess around in there, make sure you back up the original files. Setting your homescreen wallpaper, is similar to how it’s done on the iPad.

The core jailbreak apps, like Winterboard, SBSettings and Backgrounder are not working. Pretty much anything app that relies on MobileSubstrate extensions is not going to work right now. Just about everything I tried to install, ended up crashing the SpringBoard and giving me the “sad iphone” on the lock screen.

Having multitasking enabled pretty much eliminates the need for Backgrounder, but I’d be curious to compare the two. In theory, the native multitasking should be better for battery life, but which one is going to slow down the iPhone the most? The native multitasking also gives you access to the screen rotation lock and the iPod controls, in the multitasking bar.

Out of all the apps I have tried, so far, the only one that seemed to work flawlessly is WiFiSync. This app was built for release in the App Store, so I guess there’s no reason why this shouldn’t work in iPhone OS 4. I put it in my Utilities folder.

If you’re curious about a specific jailbreak app working with iPhone OS 4, let me know in the comments section, and I’ll try it out. Like I said earlier, though, there’s not much working yet. Developers are working on updating their apps, but there is no reason for them to release these updates, until the final iPhone OS 4, and the jailbreak tools are released. If you have a “test” iPhone, then I would say go ahead and try the OS 4 jailbreak, but I do not recommend doing this with your everyday iPhone.

You can follow me on Twitter: @rorypiper