I shoot an epl2 in the OEM housing with the Zen 100 dome. If you search you'll find other posts where I extol the virtues of this setup. It doesn't give you a fisheye capability, but it gives you the ability to use 3 lens in the same port (14-42 kit, 9-18WA and 60mm macro).
This is very versatile and you don't have to change the port, just the lens. You can go from a 100 degree WA view to very good macro with just lens changes. The olympus 60mm macro is superb and you will probably not be able to match it's performance in the P&S world.
I very much disagree with the comment about the size of the olympus OEM housing. It is no where near the size or weight of a DSLR housing. My bro-in-law has gone from an ikelite D300 to an aquatica D7000 and while the aquatica is smaller and much more ergonomic it's still larger and very much heavier than the oly OEM housing.
I used to shoot an older high end P&S. While my epl2 is larger than that, once you add the strobe (D2000), it's really not that much of a difference in the total package.
While I have not used the panasonic 8mm, it is considered excellent.
I would imagine your ex was shooting the kit lens on the epm1. The kit lens is ok, but I rarely use it any more. I pretty much stick to the 9-18 or the 60mm. The 9-18 is very good and the 60 is exceptional.
I also really like the ergonomics of the OLY housing. It just fits my hand well (average sized guy).
I'm sure that some very skilled photographers can get a better image from a S100 than I can from a m4/3 camera. But, I own an S95, and 3 different m4/3 (em5, epm1, epl2) and everyone of my m43 cameras will outperform my S95 very significantly (as they should). BTW, at one point I had nikon DX equipment (D50, D7000). The D7000 is excellent, but the em5 can match it or beat it 98% of the time. (note, i've never used either of those underwater).
It's the lens that make a big difference. If you're only ever going to shoot the kit lens maybe you should stick with P&S, but in the m4/3 world you have available to you 2 very highly regarded lens at opposite ends of the spectrum, the 8mm FE and the 60mm macro.
You could also go the nauticam housing route.
So you've seen first hand a big ikelite rig, a smaller P&S rig and an oly EPM1. I think you can judge for yourself the size/weight trade off of them all without other folks telling you something is big/small. The only thing you're missing for reference is an ergonomic aluminum housing for a DSLR (nauticam, aquatica, etc).
