The reason I haven't 'upgraded' to 6.2, despite testing it, is that I prefer the appearance of 5.2! As several others have said elsewhere, I find the most relevant information is presented in a more accessable way with old 5.2.
I've now running 64-bit Vista on a new PC with 2.66 GHz dual core processor and 4GB of memory, and find that I can only run Brothers Keeper 5.2G using the Virtual Machine. I've currently loaded Windows 98 into it and with hardware virtualization enabled BK 5.2G runs incredibly quickly - much faster than on my old 3.2GHz Celeron PC under 32 bit Vista!