Ill probably get an M9 a month or two after they hit the stores.
For me the big incentive is 700mhz band 12 that TMO is turning on around where i live and work. (Dallas, TX)
The only other device i may try is the Nexus 6. From here on out all my future devices have to have front facing stereo speakers.
I updated my Note 3 to lollipop yesterday and played with it a bit. The first few minutes i played a game i swore my left ear was plugged up. The it dawned on me, DUH Note 3 has one speaker on the bottom and now im playing a game so its on my right.
So the good news is im not going deaf and it re-affirms i like the front facing speakers.