I have the WOT, stock, 8 in, 5 in, the joey, and I just ordered the platypus.  The Joey is my newest coil, and I have been using it for about a month.  I like it so far.  It does seem to change the tones on the ends, but I am not sure yet if that is me, or the machine.  I haven't made any deep finds with it yet, but I think I will.  I tend to hunt old home sites mainly, so the deep signals should be there, when I hit them. 
The biggest advantage so far, is that I can cover more area in trashy areas.  I wiggle the coil around the trash, and listen for that sweet high.  I like the performance in trash.
The DETERMINING factor for me, of the joey vs the platypus, was that I had the WOT for maximum depth, and the platypus would fit in that category.  The joey was recommended to me, based upon that, by Doc's place.  I think it was a good recommendation.
I don't understand why the coil is not waterproof, and am about to resolve that issue I think.  My inclination is to use the liquid electric tape to seal it.  Some folks use epoxy to seal it.  
So, others will probably echo what I am posting.  Overall, it is a good coil, and I use it a lot right now.  I am covering a lot of area while my buddy with his puny 5 inch coil is swinging wildly to try and cover as much....ROFL.  He is better than I am, but our finds are comparable it seems to me....
HH,  Dennis