Yeah, I know it's an old subject, but I now have the capability to provide what Wendall asked for.
Got some new play toys and still had the object of last years spirited discussion in the "junk" box, so I did some analysis of the specific piece on hand.
Insertion loss on VHF is very good, less than .25 dB. UHF insertion loss ranges from about 1 dB at 470 MHz to about .5 dB at 800 MHz.
UHF signal rejection on the VHF port ranges from around 34 dB at 470 MHZ to greater than 40 dB at around 700 MHz.
VHF signal rejection on the UHF port is greater than 34 dB between 54 MHz to about 40 dB at 225 MHz with a dip below 40 dB in that range.
If I hadn't spent all my money on the new toys, I'd order a couple of other samples and test them, too, just to see how they compare.