Well the thing is although the HTC is technically capable of encoding it, it isn't an easy task for any phone. Yes, the card and the ROM all make a difference but unless you really NEED HD, I wouldn't bother. Stick to something lower and you should find it less juddery and slow.
To be honest, I never actually understood why you would need HD in a phone anyway? It's like having a really high MP camera in a phone. If quality mattered you would use a camcorder or dedicated DSLR... right? A Proper one with a good sized lens and dedicated controls. Yeah having a camera and the ability to record video is great, means you never miss a moment. But is it essential those moments are in HD? Really??
**** Local pub, 10:08 p.m. ****
Tom - "Haha, look at this guys, Harry got hit by a bus yesterday, got it all on my phone!! ROFLcopter or what???"
(they all crowd round Tom's phone)
Dick - "O...M...G... like, totally AWESOME DUDE! HAHAHAHAHA"
Tom - "I know right? Lucky I had my phone out when it happened eh? LMFAO!"
Dave (geeky kid that owns a Desire) - "OOoooooh you should have shot that in HD, WVGA is SOOO 2.1. You're such a n00b Tom, those extra couple of pixels would have made all the difference to my viewing experience you know...."
**** Blank stares from Tom, Dick and Harry (from a wheel chair) ****
Fade to black. END
Anyway you get my point. Maybe I'm wrong though...