I bought a JVC GY-HD110U about a year ago for a project that didn't get done...then there was another project that also didn't get done. I finally broke it out this week for a project that DID get done (finally).
While the 250 is slightly different, the advice that I can give you is that you really need to have some batteries...I have four, and I was on my fourth after a 2 hour shoot. Granted since the camera sat for awhile, maybe the batteries are shot, but as a just in case, bring the charger with you and extra batteries too.
Other than that, my last camera was a Canon GL-2, and I found the operation actually similar in a lot of ways. I messed with it for an afternoon, and shot the next day. So that might be my other suggestion...get some time with it and the manual before you're really shooting. You don't need a lot of time if you're familiar with cameras, but take some time.
Other than that, enjoy yourself!
Chris