At least now apparently Yahoo has thrown out $40 as the magic number, that's all MS needed to know. Now any bid around that should be taken immediately. Plus don't forget about the Yahoo investor that approached MS and asked them to increase their bid.
Watch and learn. However, if MSFT says this is their best price (take it or leave it) you might be right. That should not be the case though. They want to buy YHOO for a long time and finally they will be able to get YHOO.