Re: As someone still running Windows XP x64 ...
Despite the fact that, only last year, I did move my previous employer (a large independent school) from XP (32-bit!), Server 2003, Office 2003 to 8, Server 2012R2, Office 2013 - I can't agree with you here.
We threw it onto every PC, every client. In fact, I had one image whereas with XP I'd needed several (CPU architecture differences, etc.). I set up the image with 8 with Classic Shell, and to be honest it was pretty indistinguishable. All software ran - over 200 pieces of it - apart from a single 1990's-era Quicktime-based heap of educational junk that had never been updated and the company went bust years ago - which still ran, but crashed on a certain function. All hardware was supported (did not install a SINGLE driver across a network of 200 machines, all booted from the same PXE image) - I deleted 5Gb of old XP drivers that I'd needed for the same machines!
It all worked. And, with the fudginess of the XP-backwards compatibility, imaging and network setup, there were speed IMPROVEMENTS to running 8. Things felt, and were, faster. XP - for instance - didn't have AHCI drivers for quite a lot of our hardware and we were running in IDE mode.
We held off for ever until we couldn't hold off no more. And, single-handedly, I deployed a network of it after managing the same network on XP for many years. In one school summer (six weeks). There was nothing wrong with it. It just worked. Things just ran. And Windows looked like Windows (all Metro apps were uninstalled, for instance). On the same hardware.
I don't quite know what you're holding off against, though I admit I held a huge amount of scepticism on my own part. To be honest, if we had needed XP for anything, I'd have virtualised it on PXE-deployed images, the transition was just that easy. That's how you're going to have to do eventually, and if you use Linux underneath the VM, nobody will care - and I quite understand that kind of philosophy. But XP x64 on raw hardware? Give in, mate. At least just throw it inside a VM and admit the usage - you like the interface, not the OS running your machine - VM it and put a modern OS (any OS, even a thin-hypervisor) on the actual hardware and save yourself an awful lot of hassle. And then no disk-sector issues forever more.
Though I'm not the kind of person to dive into anything early (hell, I'm a Slackware guy and the above network had at least two Slackware servers!), there's really no reason to hold back on newer Windows except paranoia. You're used to configuring XP, get used to configuring 8 to the same depth and all the stuff you don't like about it can be turned off.
In fact, I'm about to do the same again for another independent school - same kind of size, but coming from 7. They were 8-fearers who'd even had a failed 8-trial - until they saw my 8 image. This summer I'm redoing every 7 PC to 8. We have no software that demands 8, and we have licensing which means that it costs no more to deploy 8 than to deploy 7 - but the fact that we stay on supported configurations with a long lifetime and, more importantly, a lot of new features (some of which we switch off, like Metro, of course) for basically zero downsides means that it's not an issue. And our banks are starting to make noises towards only supporting the smartcard readers on 8, and various educational suppliers debating similar.
XP was great. I used it myself for years. I'm on 7 at home. But I do most of my real work in VM's of various OS. The fact is that the base OS does not matter anymore. If you're a home user, VMWare is free. If you're an 8 user, you have Hyper-V for free - or you can just use the free Hyper-V hypervisor on the bare hardware. If you're commercial, the cost of a hypervisor software is either free (with Server editions) or lost in the noise of any upgrade.
Bite the bullet, put your hardware on something recent. Stop making problems for yourself. And admit that what you like about XP is the GUI and the working pattern. Not the OS.