TJ,
As a webhost, I would encourage you to make the switch, simply because it should all be backwards compatible, php5 scripts will run fine on a php6 server. Only realize, that if it comes at any significant expense to you, it may not be worth it. (I assume it’s not much trouble, but I only work with old-school servers, so I wouldn’t know)
As a developer who’s projects are mostly open source, with the occasional site for a non-profit, I have no control over my client’s hosting. As such it’s not feasible for me to adopt php6. A lot of developers have to apply similar reasoning to make a living. So while I will gladly point my clients to a php5 or even 6 host any day, most of my programming will be 4 and 5.
And why haven’t I heard of python3000? Python is awesome.