I have had a TPV room, a CL TPV room and a CL non TPV room (also regular standard or garden view rooms) at all the MK resorts on monorail. I absolutely LOVE having TPV from my room. If you can afford the extra $$$ it is lovely. If you tire easily, it is an easy way to still see the fireworks without battling the crowds. You can watch the fireworks in PJ's and drop right into bed afterwards. LOVELY!
I have loved the theme park view of the MK from the Poly in the past, but I am not sure that I will still like it now that the bungalows are in place. I realize that they won't block the view from the TPV rooms, it's just that they will be IN the view. I'm not sure until I see it how much of an impact (if any) that the presence of these buildings will have. My plan is to stay Poly CL TPV next Jan, so we will see then. The Poly was the first on site resort that I stayed in in WDW, and I believe that it has a very wide appeal to most people, so it is a good choice for many.
My very favourite TPV is at the CR either on a high floor (floor 11) or from the CL (12 or 14th floor). Any TPV room in the tower is excellent, however. The TPV from the rooms in the tower of the CR is panoramic of the entire MK resort areI think of it as a mountaintop experience. You will see the castle, the MK, the fireworks, the monorail loop, the GF and the POLY. You can watch the buses and boats arriving and ELP on the water at night. The magic of the CR is in staying here, not in visiting. It apparently isn't for everyone. I didn't think that I would enjoy staying here, but was pleasantly surprised to learn that it is one of my very favourite resorts in WDW. It is a contender along with the GF for my favourite resort in all of WDW.
GF TPV are also very nice, just my third choice for watching fireworks from the room. When staying at the GF I usually like garden view just as much for fewer $$$. Just had RPC MK view last Jan, however and it was amazing!