I am hesitant to say "outdated". I have a four year old DC500 and early this year bought the 1000. The main differences to me are, in no particular order:
1) less shutter lag--this is pretty big to me.
2) battery life--I have the old batteries but this appears to be solved as mentioned.
3) wider angle--I also have the wide angle lens for the 500 which also fits the 1000; I carry it but have not needed it except once or twice this past season due to the default being so wide
4) more secure/reliable attachment of the fibre optic cable for the flash and therefore more reliable flash.
5) more/better UW modes if you are not using an external strobe. I tried it once in Coz (normally use external) in about 25 fsw and was impressed by the color & clarity of the shots. That was by far the shallowest dive of the trip, don't know how it would perform deeper.
6) much larger screen is very helpful underwater for guaging composition, and also has a histogram if you want it--I find it useful because it's hard to judge exposure UW, and my strobe has a variable knob
Now, having said all of that, I only present it for information since I have experience with both. When I bought my 500, I bought the strobe, WA lens, extra battery, and carrying case (I think it was the Pro set at the time). Also came with electrical outlet adapters, care kit, etc. So this time around I only had to spend something like $450 to get the camera with housing and the rest is compatible (except the battery). I also bought an extra battery but have never needed it because the new ones are so good. If the strobe, etc., was not compatible I probably would not have upgraded. At this point I hope I am set for a while.