The tricky thing about printed catalogs is that they require some preparation, and that generally puts them into plenty of peoples' hands. One such leaky person has handed over an upcoming O2 catalog to Engadget, with the first official listing of the HTC HD2 (aka the HTC Leo) we've seen so far.
The HD2 is listed as having "the largest screen yet on a mobile", which is actually a 4.3-inch capacitive panel. Inside there's Qualcomm's 1GHz Snapdragon CPU and Windows Mobile 6.5; interestingly, rather than showing the usual TouchFLO 3D UI O2 have shown the HD2 with the Start menu open, presumably to highlight the fact that the handset runs the new Microsoft OS.
Early rumors tipped the HD2 as arriving on O2 come October 12th. However Engadget claim they've been informed that has slipped to October 26th; either way, it looks as though next month is going to be an interesting one for smartphones.