I can't quite understand why everyone is raving over this phone if I'm honest, it's majorly heavy/massive and the sharp corners will rip apart your trousers :|
How do you find your Desire HD for size? The Lumia isn't much bigger; 7mm taller, 2mm wider and about 15g heavier. The 920 is actually thinner than the DHD by 1.1mm.
Size is a slight concern of mine as well - I'm wondering if other large-screened phones only get away with it because they're thin. Time will tell I guess, but if you find your Desire fine then I can't see the Lumia causing you any problems.