Today's 9.1.1 iTunes is safe for PwnageTool&redsn0w. But those hoping to use userland JBs (like Spirit) should hold off.
In general, those using *any* userland JB should avoid iTunes updates, since iTunes can detect & remove it.
It is widely expected that the "Spirit" userland jailbreak by comex will be the first jailbreak to be released for the iPad. Spirit also provides an untethered jailbreak for the iPhone 3GS and iPod touch.