I recently started doing some tech-related screencasts for our clients (photographers) at http://bigfolio.tv.

I wanted it to be all HTML5 and I'm still experimenting. I ended up doing 3 H.264 versions (a large .mov and a large/small .m4v) and an Ogg file. Just to be safe, I put a couple download links for people.

I haven't had any complaints but I did notice that older version of iOS can't play it. Haven't really tested Android.

Getting them all converted and put on S3 is quite a PITA. Another thing I discovered–if you're putting Ogg files on S3, you have to make sure to set the mime-type or FireFox won't play it.