Zoom for the S90 to 35mm can be set in custom settings or controlled from them front ring. Once set to 35mm (or whatever required for the wet lens and housing) it is left alone. I am not talking about zooming in and out, I mean to zoom to the required setting to eliminate vignetting and leave it alone.
Agreed. It's pretty easy to bump the lever once or twice to hit the right number. (At least, it is with the Fix and Canon housings... since the Ike housing lacks a spring-loaded center, that might be a smidge tougher.) Then, just hit the lever until you're at full wide to go back to regular shooting. Not difficult at all... and if it was, the Custom setting can save the zoom level as well.
For me, the biggest annoyance I've found so far is that the camera doesn't seem to like to stay in Macro mode. Every time it auto-powers down or I change mode, the Macro setting is lost and has to be reset. My old camera (S80) would keep the Macro setting, at least through an auto-power down.