Hi Don,
I am a Nauty, Nauty boy. Just took the plunge on a complete Nauticam OM-D system, moving up from an E-PL2.
There is just no comparison between the cameras and the housings. The om-D is worlds faster and more configurable and more versatile that the PEN series, and it is built like a tank including weather sealing. It can survive a housing leak that immerses it in saltwater (but not a full-pressure flood). Faster AF, great handling, best manual exposure controls I have ever seen with instant adjustability. I could go on and on, but let's just stop at the viewfinder, which is amazing and all you need for both still and video shooting. There is never even a need to look at the screen underwater. No chimping and if you have older eyes, no struggling to focus or get your mask diopter in the right place to see the screen. By itself, the EVF takes the shooting experience to a whole different level.
the Nauticam housing is the equal of this fine camera. Perfectly placed controls and buttons, great half-press feel on the shutter release, good view of the EVF, built like a tank. There is no, and I mean no, comparison between the quailty of the Nauty housing and that of the Olympus.
If $$ are a serious concern, I would start with the OM-D with the 14-42 basic zoom in a standard Nauty port. Not a bad lens and you can actually get decent macro with a diopter. The basic port would also fit the Pana 45mm macro later on for true ultra-macro without buying another port. You can then add wide angle later. You get the idea, add things as $$ become available.
If you spend the extra to go with the OM-D now, you will really enjoy it far into the future and much more than the PEN series. It is the diference between an excellent casual camera and a full-on professional one.
Having invested my hard earned $$$ (and lots of them) to make the switch I can certainly say it was well worth it.