This has been discussed at length in a number of other threads, but there were some other issues mixed in, and I'm not sure that a proper bug report has been filed.
When connecting to an HDTV with DVI where the HDTV reports back EDID modes, the 1080i mode doesn't work correctly. It will pass validation, but when displaying, the lines are doubled, resulting in display that shows the top half of the image stretched vertically to fill the entire screen. This last worked correctly in release 1.0-8776.
I've attached a bug report. Before running the report, I used xrandr to switch to the 1080i mode from the EDID that is displaying incorrectly, and then back to my standard 720p (actually a hacked 1152x672 mode to eliminate overscan, but a compatible signal).
Perhaps related, I've been unable to generate a modeline that will generate a 1080i output that is accepted by my TV. Many that I've seen posted parse, but the TV displays a black screen. (This was true even with 8776.)