I don't have any hard definitive answers yet, but I have noticed that how well HDMI works is VERY dependant on cables and even the inputs used. Here's what happened for me.
Using Blue Jeans new Series 2 cables, the 28 ga variety for flexibility, lengths 4, 5, & 6 ft. Good for category 2 speed (the highest bit rate) up to 15 ft.
Panny BD10 player w/HDMI 1.2 into Input 1 - Works
Tosh XA2 player w/HDMI 1.3 into Input 2 - Works
JVC DVHS VCR w/HDMI 1.1 (I think) into Input 3 - Works
Pioneer DV-59AVi upconverting to 1080i w/HDMI 1.0 into Input 4 - DIDN'T WORK.
The HDMI link lights just sat there blinking, trying to sync but couldn't. It DID work several days ago on input 1, so I tried that again - no sync. Changed cables to the cheezier cable I used b4 & it worked. Changed to input 4 again with the cheezy cable - no sync. Changed to input 5 & 6 - syncs up fine.
I think it may be very sensitive to timing errors and even cable types, especially with older HDMI & DVI gear. The link light did not flash at regular intervals either, suggesting it was "hunting" trying to make the sync, looked like for whatever reason the older 1.0 spec player just didn't want to sync on that input with the new cable. The joys of HDMI
Maybe this could help explain what you observed trying your older DVI PJ.
Also, Tim, I could not get any the video parameters to show up on any HDMI input; kept flashing "Cannot Select". Very puzzling, since it shows up just fine on SVid & component vid. Then it hit me, maybe those settings are only for upconverted video, where you set the resolution, etc to match the display. It would work on HDMI then since its upconverted. But passing a direct signal from a player over HDMI, you may not be able to change resolution. Does that make sense? I don't have any experience with ext scalers so don't know what to expect. It also could be due to the fact that both you & I used DVI displays.
It'll be interesting to see if the video parameters are available with your new Sony PJ.
I'd go ahead & do the PJ upgrade. It's calling to u.
Keep us informed..