A few years ago I had trouble with Hitachi CF 8GB cards losing or scrambling images in the Canon 30D, so am now leary of larger cards.
I found yesterday that I didn't have enough memory for the large sized files, so set the T1i for smaller images. I didn't like the results, and so want to resume with the larger. But I'm hesitant to purchase large capacity cards until I hear from some of you folks. If you're using large capacity SD cards, please let me know how they're doing for you.
I seldom use video, and never did with the problematic Hitachi.
I was considering 16 or 32 GB. Though I always carry spare batteries and cards, sometimes I still run out of memory when away from home.
Are you shooting everything in RAW? I've got a mix of 2 GB and 4 GB cards and never have a problem with memory. I try to empty the card at the end of each day (or two) of shooting though (unlike my daughter who runs her cards to full with thousands of shots).
I use 2gb cards as well as 8gb on different cameras for different photos. I do that simply because I don't want to mix up butterfly photos with wildflower/plant photos (just my quirky habit). I usually download them to the laptop or notebook at the end of the day. Only problem is one of my computers won't read cards of 2gb! Dinosaur!!!