I have had similar problems trying to burn standard DVDs from HD footage imported into imovie from a Canon Vixia HF G20. I actually didn't notice a drop off in quality in i-movie, though it is hard to tell on a computer screen, but when I burned it on a DVD using Toast, there were lots of "artifacts," especially around the edges of objects. Very dissapointing considering I can create better DVD's using my 6 year old Panasonic camcorder than my brand new HD camcorder. I am still experimenting, e.g. will try using the standard recording modes on the Canon and see if it is simply a matter of standard DVDs not being able to handle compressed/converted HD footage. Does anybody out there have any other ideas?