I got a pair of PM3s. I haven't heard any Oppo phones prior to these. In fact its been many many years since I've even heard a planar phone (audeze lcd-2 in canjam LA I think).
In short they are dope ass cans. Really really really comfortable, like when I put them on I literally sighed they felt so nice. As I always said I have a large n' long head, and have fit issues with lots of headphones, no issues here. Pads are super comfy, ears fit perfectly in the cups, really nice padding on the headband and great weight distribution. Plus the pads and headband smell amazing. Best smelling headphone since the GS1000.
Sound is very midrange centric, and it is a lovely midrange. Pretty much accurate with maybe just a bit of romantic flair thrown in. Or maybe they are totally accurate and I hear them as romantic because accuracy is romantic. Nothing wrong with the highs but I'd prefer a bit more bite. You can hear the midbass just fine but it lacks slam. The lowest bass frequencies aren't very prominent at all.
Great soundstage, if I didn't know and you told me they were open cans I'd probably believe you for a bit.
As much as I love midbass slam I can overlook the lack of it due to the great midrange and outstanding comfort. I anticipate these cans getting a lot of use at work, with the V-Moda M100s going on the shelf for a while.
Only way I've used them is straight out of my Moto Gs headphone jack. Pretty easy to get decent volume out of them, although I do have the volume maxed out on some tracks that get me excited. I'll probably invest in a portable amp for the first time in my audio career because its fun to buy shit, but I am pretty happy with them straight out the phone.