That you have W2003 servers means you have systems without Powershell installed by default. You can still do PS stuff against them remotely, but unless you go to the trouble of standardizing (and keeping updated) a PS install on all of them, you will not be able to locally use PS on those machines.
Once upon a time at a job far, far from the one I now hold, I spent the time and effort to build up a set of common scripting tools and environments, and install them on all servers. I thought it would make my life easier, because I would thus have more powerful scripting tools available on all systems where I might need them. Ha! What I really did was commit myself to a bunch of extra work, keeping all those script tools updated on all those servers.
So now, I advocate defaulting to whichever script engine/interpreter is by default available and updated (updated by the OS itself, not manual means I must separately administer) on all the platforms where my scripts might ever have to run. So, if I could be certain my Windows machines were all Win7 or Win2008R2 (or later), then yes I'd begin the move to Powershell v2 for everything.
But if not, I would move to the next lowest common denominator - VBscript. And if for some wacky reason I still had NT systems to wrangle, I would move down to cmd.
I guess what I'm saying is, try to avoid building hamster wheels where possible. It may be the new shiny hamster wheel, but ... well. Your call.