I know I can force it to boot into 64-bit kernel by holding down the 6 and 4 keys during the boot process. I also know that some extensions still don't run in 64-bit mode.
So the question is what might I gain by running in 64-bit mode?
If it matters, I have the brand new 2010 15" MBP with the faster processer and 8GB of RAM.
Best Answer
With a kernel running in 64-bit mode, the kernel might be a little faster - but it's not likely you'll ever notice that.
64-bit applications run in 64-bit mode on OS X (and can access all 8GB of your RAM) even if the kernel is in 32-bit mode, so really, I don't see a point of switching kernels.