The letter was great - touching without being sappy.
I think a letter is much better than a video. For one, he can take time to compose his thought, and he doesn't have to worry about being emotional or breaking down. For another, he can write the letters now without telling Lois about them, rather than having to set up equipment that he might not have. Then, technology changes. You can always read a letter, but in few years Lois and their son wouldn't necessarily have a VCR. It's also much easier to read and re-read a letter than to watch a video. It's also something that Lois could do much easier in private. She can read her letter alone in her room without her son overhearing that Mom is, yet again, obsessing over the message from Dad.
As soon as Clark started running off to see what the commotion was about, I was sure that he'd have another heart attack from the strain. He's in quite a bad position, isn't he? He could be helping people and saving lives, but that would kill him much sooner and take away any chance that he could heal and live to save more lives later, let alone living to be there for his family. I can't fathom being in that position myself, and I hope that I never am.
Sooner or later, I think they need to issue a statement from Superman saying that he's sick, then there needs to be an announcement once he dies (assuming that Clark dies). Announce Superman's demise sufficiently after Clark's to help keep them separate. But even though there will be fallout, people need to know what happened to him. He shouldn't leave everyone to wonder whether they've been abandoned, or whether some villan has offed him, and he shouldn't leave them to hope that he will come back. Maybe Superman could write a good-bye letter to be published after his death.
