How do I construct a blaze rod harvester?

I found a blaze mob spawner in the Nether, now I'd like to build an automatic blaze rod harvester around it. Can it be done?

There are quite a few tutorials for that, and these two designs seemed most notable to me.

First design (by Etho) is complicated, expensive but fully automatic:

And another, simple one (by Generikb) that doesn't require any resources but building blocks:
_{You might want to ignore the suggestion to put furnaces there. Smelting doesn't give much experience now.}

If you want to make it even simpler but a bit more efficient, you could just put the spawner in a big solid box, then put one line of fence gates and an empty line below it. That way you'll be able to hit the Blaze and they won't be able to hit you.