Hi there! I've used the DX-3000G, DX-5000G and soon, the 8000G. If you search I have a couple blurbs ont the 5000G that I started using July (or so) of last year...
Here: http://wetpixel.com/forums/index.php?showt...9043&hl=dx-8000 and
http://wetpixel.com/forums/index.php?showt...7379&hl=dx-8000
That camera was exposed to moisture a couple weeks ago. Had lent it to a buddy for a Bahamas trip. It as in a dry bag that was not entirely dry when they had to make a swim for the boat after a trip ashore (it also was not in the housing).
Anyway, if you are used to the MX-10 the size and shape will be familiar to you. The size, by the way, is one of the reasons I use a small point and shoot. I also have a Rebel XT SLR but taing it underwater an expensive hobby I haven't talked myself into yet. The point-and-shoots are less cumbersome than a SLR housing and strobes and much less expensive, but you lose some control and quality I think. I have had good luck with the 3000 and 5000, though, and would recommend them. I also use the camera with the small, YS-25Auto strobe, which I would recommend. I'm not fond of the fibre optic stobe sync cable, though, as I have managed to break two of them. I think some of that is due to cold water making the plastic brittle and the fact that I'm probably not as gentle the thing as I could. I also have the wide angle lens. I like the WA lens but if you are into macro you might do without.
I have not tried the 8000G yet but I leave for Truk on Friday! Physically the 8000 is the same as the 5000 and the cameras themselves are very similar in function. The most notable difference I have found is that the 8000 camera does not do RAW (well kinda, it has a TIFF setting) but RAW on these cameras, even with a fast card, is very slow (15-20 seconds to write the file to a card). I tend to the highest quality JPG mode due to the speed.
By the way, the cameras in these housings are Ricoh cameras. The 8000G is the Caplio GX-8 camera, the 5000G the Caplio GX. I have found that the Ricoh cameras are not popular in the US and hard to find. Ebay will bring up some in the UK and Japan but very few in the US. If you should need to replace a camera it may be a challenge to find one (which is why I now have the 8000G!).
I have some shots online if you would like to look: http://dbeedle.com . All the UW shots are with the DX-3000G except the Tobormory shots. Those are the 5000G.