One thing about the Intel switch hasn't been discussed here:
Apple needs (and wants) to protect the Intel version of Mac OS X, so that it will only run on genuine Apple computers and not on otherwise compatible industry standard PCs. To do so, they will have to put some kind of protection in the kernel. It will be much easier for hackers to disable this protection if they have access to the kernel source code (via Darwin). So has Apple already confirmed that Darwin will stay open source even after the Intel switch?