Microsoft really has done a great job with Windows XP Home Edition and Professional, especially in the quality and level of support for plug and play (PnP) compatible hardware. Nevertheless, you may stumble across the occasional problem with XP installations as I did with both legacy and new hardware.
For one thing, shared IRQs are perfectly OK with PnP (as long as the underlying devices, usually PCI-based, report themselves to be OK with such sharing), but may sometimes produce flaky results. I've installed XP on about 20 different systems at this point, and have run into problems with 2 systems. In each case, a shared IRQ turned out to be the culprit: in one case, the PnP handler defaulted to sharing an IRQ between a SCSI controller (with 4 devices attached) and my primary SVGA card; in the other case, my primary NIC and a SCSI card were also sharing an IRQ. I went through numerous blue screens, some strange network and component failures, and other odd symptoms before checking the IRQ layout. In each case, I fixed the problem by assigning one of the devices that shared an IRQ to a different, open IRQ.