Stack languages look really cool to me. I have no idea whether they're practical.

For language beauty, the ones with simple syntax (e.g. Lisps, Forth, q) win. However, for a large production system, I'd be more inclined to use something with static typing.

Static typing falls down in a different way with large systems-- compile speed-- but if the thing's not being changed on a regular basis, that's not a huge issue.