The best height is one that does not require you to lean over very far to use the controls or lean over to put pans in/take them out of the oven cavity. (Keep in mind that pans are usually quite a bit heavier once they have food in them -- it's not like storing an empty pan.)

The real idea of a wall oven is to put the oven at a more functional height, not less functional. After all, if the lower height is OK, then why not just get a range -- it's less expensive and you don't lose the counterspace you're worried about losing?

For most people, that means mounting the oven higher than you find in a range but not so high that you have to reach too far up for the controls or pans.

We considered an under-counter wall oven when we remodeled, but our KD showed us one installed and we immediately nixed the idea. The oven is lower than the oven in a standard range and, when open, the oven handle barely missed hitting the floor. Now, we are a tall family, but even my 5'6" mother thought it was much too low.

In addition, as you get older, do you really want to have to lean so far down?

I recommend you go somewhere to see one installed and take a heavy pan (or pan with something in it to make it heavy) and try to "use" it.

Ovens that are part of a range are designed to be accessed at their low location. Even then, some people dislike having to bend down to get to the oven. On the other hand, wall ovens aren't really designed for under-counter installation. They frequently feel too close to the floor. They also often vent hot air just where you are standing (although that can differ between models).

If you have a wall oven, I would normally recommend installing it at about counter-top level or no more than a couple of inches lower. You could also install it a little higher, but if it is too high, again, it becomes difficult to access.

On the other hand, if you think that you only use your oven very rarely, then obviously none of these considerations matter much. For the once-a-year turkey, it really doesn't matter if the oven is somewhat less convenient to access.

On the other hand, if you do have an easily accessible oven, you might realize that it can be used for a lot more than just roasting turkey. Many commercial kitchens use ovens for the bulk of their cooking. It's a great option for slowly braising foods. Much better temperature control than using a stove top. It also can be used to keep dishes warm before serving.

Personally, I find that after having learned about the usefulness of an oven, I actually need more than one oven to efficiently cook larger meals. Of course, for simple everyday meals, all of this is moot, and I can do with whatever limited tools I have access to.

Funny that you'd mention swapping dining room and kitchen. That's exactly what we did. We went from a rather awkwardly shaped kitchen, to a beautiful and functional galley kitchen. Unlike most galley kitchens, we actually managed to have a functional island by placing it just outside of the core part of the kitchen. It does double-duty as an extension of the dining table in our new dining room. I love just how much better things flow this way.

The island gave us a place to install less-frequently-used appliances outside of the kitchen but still within easy reach. In our case, that meant that we put the freezer under the island. The space that we gained allowed us to install proper wall ovens.

Of course, as you customize the space, things do get more expensive. That's always a problem in remodels. But this is likely to be our forever home; that makes it easier to justify doing it "right".

My daughter did a GE wall oven under her 30 inch cook top and loves it. She is only 5'2". Works for me too. 5'4". I haven't heard her husband complain. He is 6'.

I have a Miele 24 " CSO and a Miele 30:" oven next to it and both are under the counter. I love the placement.

We went from double ovens to ovens flanking our range top under the counter. There's a toe kick drawer under each oven. Great spot for an extra oven rack, broiler pan or large trivets. Ours kick to open so no bending to pull open. We like the counter space above the ovens.