No, Apple's Aperture product will not run on Windows.
It relies heavily on some of the Mac OS X API's and technologies (CoreImage/Quartz Extreme) to get the performance it does. Some of the effects and how they're done in real time are achieved by offloading some of the computational work to the GPU (graphics card). It's the same for other pro products from Apple (Final Cut Pro, Motion).
Mac OS X fits nicely for what I do - some graphics work, a desktop system that plays nice with the rest of the organisational culture (MS Office/ Exchange integration) and I have a decent unix box as well (which is the important part as I'm a unix admin

. I've got both a dual G5 2.0GHz with 2GB RAM + 20" Apple Cinema Display and a PowerBook G4 1.25GHz
w/ 2GB RAM. Both run Adobe CS well, and my evaluation copy of Aperture should arrive next week.
The Cinema displays are just a whole lot of wow. Colour accuracy when profiled with ColorSync (OS X built-in colour calibration) is spot on.
The Adobe products are fairly identical on both Windows and Mac, however the Mac versions often have a slightly more polished feel. The performance is about the same when using the optimisations for both (P4/SSE3 and PowerPCG5/Altevec). Some times it can be better in ideal benchmarks (but I don't want to go there... the real world is a different place).
Deciding if Mac/Windows/Linux suits you is like deciding between Nikon/Canon/Pentax-Olympus-Minolta
