i use sony hc5 and i have noticed same things...
i think it's due to the hdv format limits, but isn't really good to see slow motion with still images before and after..
i just decided to use 16:9 dv quality for tandems to linear edit videos, and use hdv quality for other videos...just to have it in high quality when acquired on computer...
because anyway if you don't have a hd tv, you always see it converted in dv during play, on the fly...
anyway registering in dv format with my hc5 give really good shots, much better that with other dv sony cameras...such as pc1000 pc 107...