Handheld Learning - learning with mobile and ubiquitous technologies

I hadn't realised that there was such variance on speeds for SD cards but at least some of the cost differences between them now start to make sense.

Do you have a feeling on how much these speed differences effect day to day use of a PDA?

What speeds/latency would be minimum, say, for video, etc?

I guess what I'm asking is that if we buy the cheapest, slowest cards is that going to be a false economy?