Although everything I read about the 5D3 literally yells "BUY ME NOW", I learned to wait until most of the 'bugs' are out of new products before buying one.
Back in the 70s when I was installing new versions of IBM mainframe operating systems (new versions of Windows, to you young 'uns), I waited until 4 or 5 'updates' were made to the new operating system before I installed it. It was mostly problem-free by then. Likewise, I wait until at least Service Pack 1 comes out before going to a new version of Windows. Even better if SP2 comes around before I make the move. The same is true with cars and a major body restyling...wait another year or two. I got bit on that one back in '96 and went through too many problems and recalls before I traded it for a '98 two years later.
Even with the high price of a 5D3, I -really want- the superior focusing and ISO performance NOW! But experience has taught me to wait...at least until next March or so when I get my tax refund.