I haven't bought the S&W M&P Detroit police trade in guns from Buds, but I have bought from them, and I've checked out the police trade in M&P40c's several times.
I've had good service from Buds so far. I bought my .45ACP SIG P250 Compact from them and last weekend I bought my S&W M&P40c (new) from them. The M&P40c took longer than I'd like/I expected to ship (they just shipped it yesterday) but it wasn't unreasonable. I should be able to get to my FFL to see it and fill out the paperwork early next week, but I have no reason to expect the gun to be anything but perfect. From what I see in reviews on Buds and elsewhere online, if I do get a less than perfect gun, Buds customer service is terrific.
As for the police trade ins, the unissued are just that. They are brand new guns at used gun prices. The issued guns seem to always be in better shape than people expect based on the category they buy. I didn't go with the trade ins in the past but came close. This time, I didn't because: 1) they only have the full size and I wanted the compact, and 2) because I got my brand new M&P40c for $345 (though I don't have night sights).