Actually, I believe Crossing Jordan is doing pretty good in ratings. And, I think the same is true for Las Vegas. So, I really don't see the point in doing the crossover.
I watched Crossing Jordan yesterday (because I usually do anyways) and I think this whole crossover thing was pointless. There just wasn't any chemistry between the two casts because their show styles are too different. The characters on Crossing Jordan have all sorts of personality disorders (ex. neurotic), so they tend to be wackier. Whereas on Las Vegas, their personalities are tamer because they aren't written to be cartoonish, but rather more normal.
In yesterday's ep, Danny and Sam stuck out like a sore thumb on the show. You've got all the other characters being weird and when you hit the guest stars... nothing. The same happened for Woody and Jordan when they showed up in Las Vegas near the end. Their weirdness didn't fit in among the evironment.