Sorry, but every time I hear someone say the camera they're selling only has 30 (or whatever small number of) hours on it, I think back to the one time I was dumb enough to buy a used car from a lot, and the salesman told me "But those are all highway miles". :D
Seriously, if you know the guy personally and trust him, the XL1 is comparable to the XL2. Otherwise, just buy a nice new XL2.
However, keep in mind that Canon prosumer cameras are notorious for developing head tracking issues. As such, a used camera has a VERY high liklihood of needing service soon if it's more than a year or two old, which is likely if it's a straight XL-1.
One nice thing about the XL2 is that they have finally installed built-in XLR jacks into a camera, so no need for the trusty MA-300 on this one. The stock lens has better zoom, and the camera has a better Lux Rating, but all in all, you're still looking at the same CCD board, and the same lens style, so picture will be about the same. THE extra cash just gets you extra features that make life easier.
So I suppose what it all comes down to is how easy do you want life to be, and how much is that worth? :-)