This is the steel I use in my oven -
http://bakingsteel.com/shop/the-big/. It does take some time to get hot (it is very thick.) It is also very heavy - about 30 pounds - but if I drop it, it won't break (of course, the wood floor or my toe WILL break...
)
It does a better job of making a good crust in my oven than any pizza stone has done (I've tried several from the cheap to expensive.) The limitation is still the temp my oven can hit and hold - the steel does hold heat very well, but it can't manufacture heat. That's why I am looking forward to the Uuni.
However, for a cooking surface in my oven for pizza, bread, and other meals this is hard to beat (and lift...
)