The much lauded and much anticipated update to Mac OS X, Leopard, is sadly being delayed. Version 10.5 of the OS is being pushed back an additional four months due to Quality Assurance concerns - but not QA of OS X, but rather Apple's iPhone which is expected to ship this June. While there were some rumors of an OS X delay due to Boot Camp, from the horses mouth itself we hear the truth:

However, iPhone contains the most sophisticated software ever shipped on a mobile device, and finishing it on time has not come without a price - we had to borrow some key software engineering and QA resources from our Mac OS X team, and as a result we will not be able to release Leopard at our Worldwide Developers Conference in early June as planned.
Instead, Leopard will supposedly and hopefully be available in October. According to Apple, it'll be worth the wait. Then again, many companies have histories of releasing software too soon and having it come back to bite them. Better late than never, and better be safe than sorry.