The just released limera1n promises to jailbreak iOS 4.0-4.1 on iPhone 4, iPhone 3GS, iPad, iPod Touch 4G, and iPod Touch 3G. It's Windows only for now, with Mac & Linux support coming soon.
I have an iPhone 4 (got launch day and only updated to 4.0.1, but I don't know the baseband; I don't really care because I'm using AT&T.). I updated (not restored) to 4.1 and ran limera1n; The process completed successfully, and I turned on my phone. I clicked the limera1n app (white icon) and the app opens, I can see the raindrop in the red circle at the top (see pic), but then the app crashes. I tried re-running the limera1n program on my computer 3 times and all I get is a crashing app..... Any thoughts?