READ THIS FIRST!
That said, here is my experience with Grub2 and Arch Linux on a Windows 7 machine.
I don't know about OSX, but I was able to install Grub2 with Arch Linux on a Windows 7 machine using the traditional BIOS (MBR) boot.
I did have a problem one time with too many primary partitions. Generally speaking you can only have 4. I had 2 primary partitions that were created with the Windows 7 install and another primary recovery partition making 3 altogether. I had to take the remaining space and create an Extended Partition (the 4th primary partition) in it with several logical drives - and installed a different distro on each one.
I also had a problem installing Grub2 from the Arch installation CD because it would not create the proper partition type for Arch. Running fdisk -l showed the partition as FAT16 instead of Linux. I ended up creating and formatting the partition while booted into Mageia, using MCC, then I installed Arch and Grub2 successfully.
When you install Grub2, you probably want to install it to the MBR (I imagine this is true with OSX as well as Windows).