OK, did some more digging (I always research things to death before making the leap). and found a couple things. First this interesting review:
http://www.cheftalk.com/forums/cooking-equipment-reviews/8935-hearthkit-oven-insert.html
that says this:
There is a review on The Hearthkit Oven Insert in this month's Cooks Illustrated. I was glad to read it since I was contimplating purchasing this item not only for myself but for other foodie friends. Here's the scoop: they tested the insert on various breads, cookies etc in their commercial Wolf ovens and the testers were indifferent in the results. However, when the insert was used in a typical home oven the results were greatly improved over not using the insert. So for all those who have nice convection, DCS, Wolf, Viking, Gaggenau, Thermador etc. you probably will not see any difference in your product using the Hearthkit so save yourself some dough here. But, if you do not own one of these high-end ovens it would make a nice addition to your kitchen
Also, Peter Reinhart the Artisan bread cookbook writer raves about them too:
Peter Reinhart, noted chef and author, wrote to me about the
HearthKit explaining it
"goes a big step beyond a pizza stone, essentially turning a home oven into something akin to a brick oven ...I really am convinced it makes a huge difference in everything you use an oven for including meats, fish, chicken, and pastries-not just pizza and bread..."
But I found this really, really interesting from here:
http://www.bread-bakers.com/archives/digests/v102n031.txt
Subject: Baking Stones
Date: Mon, 15 Jul 2002 08:08:17 -0400
Perhaps I'm old fashioned, but rather than a new-fangled baking stone, I
simply use quarry tiles, which any good tile store will carry. 6 of them
are sufficient for a standard oven. I use cornmeal to prevent sticking.
I'd let you know the price, but since I've had mine for 20 years, I can't
remember!
Using these tiles, I get great crust on artisan breads thusly: Beneath the
tiles, I include a dry baking pan containing gas-grill briquettes (don't
crowd them) as I preheat the oven to 50 F above baking temp. When the
oven's preheated, I pour one cup of boiling water into the pan, close the
door, and drop the temp to the baking target. I don't touch it thereafter,
no spritz, no sprays, like I mean, nada. This holds the oven to temp and
contains the steam. I've read separately that oven temp drops 50 F every
time you open the door. (Cover the oven-door glass with a dry towel to
prevent spills from cracking it. Remove the towel before closing the door!)
And this, from here, also really interesting. You really should follow this link to see the amazing photos and discussion following. Now, they wre specifically talking PIZZA over breadbaking, but it's the same concept and idea as the lady above... cheaper, but probably harder to take in and out, though smaller to store since it's small tiles, versus a big insert.
I WILL say, be careful that you buy the right tile so that you aren't poisoning yourself!:
http://www.pizzamaking.com/forum/index.php/topic,440.0.html
I made my own "HearthKit" insert for my electric oven by putting two
layers of quarry tiles on a rack, then leaning more quarry tiles
against the upper rack to create walls. All of this thermal mass
provided stored-up heat energy which radiated back to the pizza which
cooked the top and edge of the crust.