I just spent a week trying all variants of PO on my wrist while on vacation in St. Thomas USVI. I'm starting to feel that an affordable diving watch may deserve a place in my collection. I have two Glashutte Original watches, both with non-metal bracelets, and it's becoming evident to me (in terms of my personal lifestyle) that having a "wear anywhere" watch that I can bring to the beach, swim in and do manual work in, may be worth owning. Thus the PO as a candidate.
That said, I agree with the positive statements made here about the PO. It's a terrific watch and now has a really great movement/escapement inside.
Regarding the issue of 42 mm vs 45 mm case, I tried-on both. I am 6'1" and am a fairly big guy (not overweight, mind you, just not exactly dainty). My wrist is not "NFL football player" thick, but by the same token, it's not exactly "girlie-man" either. When I tried on both, the 45 mm filled out my wrist in a way the 42 mm didn't. So, for me, I prefer the 45 mm. That said, I understand that Omega is using some form of bracing for the movement in the 45 mm since it's a slightly larger and roomier case. I was counseled by one person I trust that some "purists" might view this as a negative, but I really haven't heard that from others I've spoken with. My AD (with no axe to grind) speaks very, very highly of the Omega coaxials -- clearly he would steer me toward the PO and away from the Rolex SM/SD for exactly the reasons pointed-out by Art.
Regards
David