720p24 on the D300s is only about 160 MB/min and you're limited to 5 mins, so I don't think the particular size of SDHC is a major consideration. I've yet to buy any compact flash, but haven't had any issues with video on my Transcend/Patriot class 6 SDHCs.
Thanks.... I would like to point out one thing; the limitation is 5 minutes, however that is 5 minutes per session, not 5 minutes in total video. The interesting thing to me is the SDHC capacity is amazing to its actual size, say considering CF cards.... I am not an electronics person so that may seem simple, but to me it is truly an amazing engineering feet.
I realise that's 5 mins/video, but my (perhaps vaguely expressed) point was you'll be slaving over the camera just to fill a small card. It also doesn't give latitude for leaving the camera recording unattended over extended periods to fill the card.
Is it really only 5 minutes? I guess I never looked closely at teh clock in the videos I've taken with it. My D5000 will go for 20 minutes per session. That's a big difference (although in practicality it's not much of an issue). I wonder why the difference though.