Pros:
Able to go over 4 GB ram. Faster rendering for 3D and music studio software.
Cons:
Driver support for x64 is rare. Some games are not 64-bit compatible.
The Bottom Line:
Good for studios and an alternative of Vista 64.
Overall Rating:
Author's Review
Much of my studio software walks the edge on the 3 GB ram limit and that same software is not compatible with Vista, yet it works just fine XP Pro x64. Perfect for compiling high quality music when you need to go over the 4 GB limit which 32-bit restricts to.
Gaming in x64 is a pain, and driver support for x64 is very rare. I got my Windows XP Pro x64 through a school bundle and set up a dual boot for the Windows XP Pro SP3 and Windows XP Pro x64 SP2 versions on my studio computer just because of the compatibility issues.
I don't recommend the x64 version of XP isn't for home users who are just using office and the internet. They are better off using just the plain XP 32-bit version. I only use x64 when I need to go over the 3 GB restricted limit of XP 32-bit.
Another handy thing about x64 is faster load up time for applications and the operating system itself. It also has fewer security holes than Vista and is the mirror image of the 32-bit version of XP so all your favorite features are still there and easy to get to, that is after you do a full install. Upgrading from the 32-bit cannot be done and requires a clean install, meaning you must install what ever is compatible in x64 again.