I know from experience with a T2i and 60D that card speed for SDHC makes a big difference for video. However I have no experience with compact flash cards. Moving up to a 7D but my fast SDHC cards will do me no good

Any recommendations on specific brand of cards and speed you have had good luck with?

Do I need 400x, 600x or is 133x sufficient for video?

Thanks for the advice

I haven't done a whole lot of video off my my 7d, but 400x (SanDisk Extreme, 60mb/s 16GB) seems to be sufficient for me. If you plan on shooting in 1080p, you're going to want a lot of room though. Averaging from two videos I did over the weekend, I'm getting .33GB/minute.

Transcend 400x 64gb is sweet and trouble free.
delkin 450x is cheaper, but I haven't tried it.