but you still not answer did im need mac or i can use windows
I can confirm it does work, but since it is pwnagetool based it is Mac only. I would not recommend anyone tries this themselves unless they understand the process which is described on redmondpie. It is not really for those who need their hand held at this stage.
The end result is buggy at best, and as stated, is really only for developers of jailbroken applications who want to get a head start on compatibility issues. Many things are still broken.
The general populous IMHO should leave it alone until a stable JB for 4.2.1 public is released in the coming weeks...
Hope that helps.
I'm sorry, but you are once again misinformed. Yesterday you posted on another thread that there was no way to jailbreak 4.2/4.2.1 for iPad - even though the devteam had already posted the new version of redsn0w for that very purpose. Today you are saying that 4.2.1 is not "stable" and "buggy at best (which is just something that you read on another website)".
For anyone who wants ACTUAL FACTUAL information - the redsn0w jailbreak released yesterday for 4.2.1 is not buggy, and the jailbroken system is PERFECTLY STABLE, with no battery drainage or anything else of the sort. The only single issue is that you must patch cydia afterwards in order for it to work without crashing before loading.
I have been running jailbroken 4.2.1 on my iPad, with Cydia, and have not had a single issue, nor have I noticed any bugs.
Follow the tutorial at redmondpie and you can't go wrong. Also, since it is a GM and not a final version, you will be able to downgrade to a lower version without any trouble at all.