Alex
Your points are well taken There is a certain sense of self-congratulation by owners of this lens... once you spend the money required to purchase and convert this lens, you had BETTER be happy:)
I think for me part of the attraction is the form factor. I don't own a Superdome, but I find the 13mm very easy to handle, both from size and bouyancy considerations. It doesn't take up much room in the camera backpack either.
I've never been in a shark cage, like Matt, but I believe it would be easier to handle this optic in close quarters over a large dome set-up. Especially the retreat:)
I have only really used my 20-35mm in the pool. It is very sharp indeed. Now, that's not so easy with rectilinears. I did take it to Bonaire last Feb but at that time I was using it in a Nauticam. I had a gear adapter made by a local machinist. Due to the very forward position of the Seacam gear relative to the Nauticam pinion, while it would zoom on land, once the housing compressed, the gear adapter would bind and became inoperable....
So, I replaced the Nauticam with a Seacam D800. The zoom works perfectly in the pool.
I will see how it performs in the Solomons in Nov and report back:)
Ian