Really depends on how FUBARed your current install is. I've actually had the same XP Pro install for, oh, 2 years and 3 motherboard/processor upgrades now, and a couple of hard drive Ghost jobs in there, too. Totally stable, no performance issues...
The key thing is to uninstall all of your major peripheral drivers (video, sound, motherboard chipset, network) and also delete all values in the HKEY_LOCAL_MACHINE/SYSTEM/MountedDevices/ key folder if you're not reusing the same drive. Let me explain. Hehe.
Once upon a time, I was a very, very bored man with an Athlon XP 3000+ coupled to an nVidia nForce2-based motherboard. I was upgrading to a 64-bit system, and like you, DJ, I had a crapload of software I didn't want to have to sit down and reinstall. All I did was uninstall all the core peripheral drivers -- motherboard chipset, video, audio, etc... Basically, anything directly related to the PCI bus. It also helps to run an app like DriverCleanerPro ( http://www.drivercleaner.net
) from Safe Mode afterwards to get rid of any lingering files. I was still using the same video and sound cards on this run, so I didn't really bother; it bit me in the ass the first time I restarted and Windows recognized some of those remaining drivers before I'd completely uninstalled the rest
of the crap.
Anywho, after all of this was done, I just installed the drive in the new system. XP gets f***ing pissed when it sees a hardware change of that magnitude, but it's a pretty robust OS. Kids, don't try this on Win98. You'll have to reactivate within 3 days if you have SP1 or later... If you're running a cracked version, you're probably in for some comedy -- depending on the crack, you can probably get away with just re-entering your confirmation number AFTER the second reboot.
After everything is up and running (click Cancel on any "New Hardware Found" windows), reinstall your drivers. If you really have been maintaining your OS well, you shouldn't notice any issues with it, e.g. slowdown, etc. The only thing I've seen on mine is a bit of flakiness in the Networking control panel, as I've used the same static IP on my box for every migration, and it doesn't appear to have removed any of the old network adapters from the registry. Nothing more than a, "Hey, this IP is assigned to this other adapter, which isn't physically in the system... Are you sure you want to use it?" message every time I tweak my TCP/IP settings. Meh.
As for what I said about the registry entries above... If you're Ghosting a new hard drive, do that right before you run Ghost. The reason is that Windows will try to enumerate the Ghosted drive with different drive letters. BIOS will try to boot to the drive, but once Windows takes over the boot process, it will go looking for drive C: and not quite find it. All your data will be there, but under the wrong drive letter. If you kill all those mounted device entries, on its first boot, it will automatically assign the drive as C: like it's supposed to. I learned this the hard way a couple of years ago. Hehe.
As for performance differences, none. I've been doing this since late 2003, and I haven't had a BSOD or any issues beyond the Network Control Panel warning message. I did
discover that nVidia's release IDE drivers for the nForce2 platform suck donkey genitalia, resulting in a re-ghost to fix a half-corrupt hard drive... But that's another story. Usually performance issues will be a result of "registry bloat" -- uninstall your drivers, and you'll minimize a lot of it. BSODs would be a result of low-level junk like old motherboard drivers still floating around when the OS tries to detect the new system... Bad ju-ju.
Bottom line: it can and does work. You just need some patience, some basic knowledge of Regedit, and a set of cajones like a pair of cantaloupes. Good luck. (Are you still reading this? lol)