You really need to read the threads on the forum as there has been plenty of discussion about this and a lot of it is down to personal opinion.
* What is the best hard duty protective case for HTC Desire?
I lost so many cases but at the moment i am using the official HTC Desire slip case, this is not a heavy duty case as such as you need to take the phone out and once its out its exposed
* What is the best screen protector for HTC Desire? I've tried using screen protectors in the past but they were always hard to put on and had bubbles, what is the best and easiest to put on protector out there?
Not sure what the best is but i use the official HTC one which does the trick, £5 for two on play.com
* What is the best dock station and is there an inductive (wireless) charger that supports HTC Desire?
no inductive but i use the dock station from expansys
* What is your favourite and most functional bluetooth headsets, fully supporting HTC Desire? I am eyeing Nokia BH-905 as an insanely long-living and powerful headset. Is it fully operating under Android/HTC Desire?
i use the MW600 but i also have two jabber headsets that work perfectly. The newer bluetooth headsets with music player displays will not work right until android supports (or there is a driver installed) to support the tags.
TBH all non bt devices that are not music related will work just fine with the headset as they will all use the bt standard.
Rooting DOES NOT void your warranty if you are in the EU!