For me the blast furnace feels like its a bit of a useless feature. One there is not a lot of ores that can be used with it.
Two unless you have a large need for tons of iron or have a large scale iron farm then you probably not even bother using it.
Three the food furnace is a lot better then the blast furnance since there is a lot of foods that can be cooked with it.
Four why would I replace the original furnace that has been in most editions of minecraft when it works decently fine.
I'd like to see the blast furnace setup to handle stone type blocks instead. Why because you have a variety of stone you can work with.
There is nether brick, stone, cut stone, smooth stone, brick, glass, etc..
This would help the player get a home up really quickly since that is a bit more important in early to midgame since the player is not going to have a lot of iron lying around. For me I don't even bother using the blast furnace.
Still I like to hear what you guys think.