ONE WORD PERFORMANCE…

You want some reasons to upgrade past XP to Windows 7.. How about these..

Here are some killer facts about Windows 7 that are compelling reasons to update your hardware and software..

DX COMPUTE (hello general purpose parallel computing using the GPU automatically)

http://www.guru3d.com/article/computex-2009-day-0-before-it-all-begins/4
Windows 7 has DX compute embedded in its core and as such the GPU can now completely be opened up to the operating system, assisting applications that would like some parallel computing capability using the CPU and GPU together to improve applications speeds (not just graphics). If you know what CUDA is, DXCOMPUTE is basically a more advance version that is completely integrated in with the new OS..

BYE BYE DISPATCHER SPIN LOCK

One very important change in the Windows 7 kernel is the removal of the dispatcher spin lock and redesign and implementation of its functionality. Eliminating the dispatcher lock and replacing it with a set of synchronization primitives and a new "pre-wait" thread state, here. The direct result of the reworking of the dispatcher lock is that Windows 7 can scale to 256 processors. Further, this enabled Microsoft to tune the Windows Memory Manager to be even more efficient than it already is.

Those two things alone will drastically change Windows performance and already does..

DIRECTWRITE and DIRECT2D

If you want to see something more close to home check out the beta of the new version of Paint.net (which is very much like Photoshop or Paintshop Pro) which enables the new text rendering API (Direct Write)..

DirectWrite enables better readability, adds support for a large variety of languages and scripts, and in conjunction with Direct2D provides superior rendering performance for Windows applications. Applications can also use DirectWrite with GDI and carry forward existing investments in the Win32 code base.

You will see a drastic speed increase in text updating and display on all Windows applications run under Window 7..
Also direct3d has already been integrated with Aero for sometime for WPF applications since the .net framework 3.5 sp1. We are just about to get Visual Studio 2010 and .NET 4.0 with other goodness..