Silago and Scorpiofish,
The Ikelite is a good housing, but I think when you compare its controls to one of the aluminum housings, you will see what I mean by "sloppy". Perhaps a better choice of words would be "looser". However, if the budget is the primary concern, Ikelite is the choice because it is definitely cheaper. Depending on where you buy your housing, there could be a factor of two in price!
I happen to prefer the aluminum housings, but as I said, they are more expensive. If Aquatica does survive, that would be great; but the last I heard, they still had very large financial problems. That is not a good place to be in the current economic climate. However, the housing is a good one. Even though the Sea & Sea housing for the N90s has been discontinued, some dealers still have the housings in stock. If that is the camera you have, you may still be able to find a S&S housing. The Subal is very expensive, but I liked the "feel" of the controls from the very first time I picked it up.
Again, my suggestion is, if you can, try them out and see for yourself. One more thing: use the housed camera above water until you get used to all the controls. You can do this in the privacy of you home; and that may be the best way to do it. Compared to the NIkonos-type camera above water a camera/housing combination is very bulky and heavy! If you are currently a Nikonos, MX-10 or MxII-EX, etc. user, you may find that the switch will take some time. In my experience, housed cameras are, at first, more complicated than their non-housed brothers. But once you get used to them, they are more versatile.
SF