Like everybody else that has posted so far, I think you will be very pleased with the 3D. I looked around for a while and finally found a low 1021 serial number CZ3D in pristine condition and sent it to NASA-Tom to make sure it was properly tuned. Tom put the Nickel window back into spec and made a few other minor adjustments and now my 3D is turning out to be an "old" coin killer.
I took the freshly tuned 3D to a small school yard that is close to home that I have literally hammered with my F-75 and F-70 and found 5 old nickels, 2 silver dimes, 5 wheats and a few clad coins in just over an hour the first time out. I know the numbers don't sound significant; however, this particular school yard is very small and I made the finds exactly where I had been previously with the F's. I just ordered the 10.5" Spider coil today so can cover a little more ground and get that extra inch or two. Since switching from the F-75 to the 3D as my primary detector, my silver and nickel count has gone up significantly and I no longer need to worry about EMI. The down side to the 3D is that they are a little heavy by todays standards but still manageable when pole mounted.
Good Luck with your new 3D and don't forget to write and tell us how you are doing.
Leo