When I bought my P5 I asked the used car dealer if they could remove the factory deck for me before I even took delivery. I had the wire harness all done up for my Pioneer MP3 deck and installed it right in the Futureshop parking lot after I bought the mounting bracket.
I got the pocket style which, if I remember correctly, just clips in without any bolts or anything. I put it in with the pocket on the bottom and the deck on top, which I didn't like, and reversed it with the deck on the bottom and have run it like that for nearly 3 years now.
I'm not a fan of what most other companies sell and have bought nothing but Pioneer for a long time and they've all been great. My last ones ribbon cable (flip down face) broke from repeated flexing, but I ordered the part, soldered it in, and it continued to work fine. No skipping or anything.
Newest one, which is still 3 years old, is still going strong. It's gone through the hottest days of summer and the coldest days of winter (-30c/-22f and below) without problems. The only time it's ever acted weird was when the volume dial wouldn't work, but I removed the face plate like I do every day, ran my finger over the metal contacts where the face plate touches, and that fixed it. Must have been some dirt or condensation on the contacts.
My brother has a Pioneer with Ipod interface for his car that he loves.