Seriously. I remember trying out the preview version on my then-XP-running PC back in 2009, and being blown away by a) how much easier it was to install and get going, b) how well it ran all my existing software, c) how it let me finally use all of the memory installed in my machine, d) how much better it was than Vista. I pre-ordered a copy soon after, and the rest is history. Now, on my Mac, I have my Windows 7 VM for running various applications I still use.
Installing Windows XP today is not nearly as fun as you might think, particularly if you've got a pre-SP2 copy. When I tried it, I had to manually install some patches just to get Windows Update working, then some more before I could install IE8, and some more before I could install MSE. And then all the patches to bring the whole lot up-to-date - that took hours and hours to finish. I'd only recommend trying it if you're installing onto a machine that you don't actually need to use for a good while.
As for the 'but it's tried and tested" argument for hanging onto XP, I would point to the number of flaws that are still being uncovered in the Windows codebase, many of which are also in XP. Yes, you can mitigate against some by hardening your system, running only as a standard user, etc. - but for most current XP installs that will probably mean extra aggravation caused by third-party software written back in the Bad Old Days that expects to run with full admin privileges.
The only excuse for continuing with XP, to my mind, other than sheer obstinacy, is where you've got systems that absolutely, positively require XP running on physical hardware - specialised hardware or software that won't work via a VM because they need direct access through physical ports. Such systems should be segregated from local networks and the Internet as much as possible.