I tried a P155 and liked it, but would appreciate comments on the P155, as well as alternate suggestions.

My requirements are:

realistic piano sound
realistic piano touch
easy to store vertically when not in use
tunable
supports temperaments
under $1500

My impression (in a noisy store, with the keyboard mounted in an awkward position) is that the P155 fits all the requirements -- though I would have preferred a more authentic touch. The touch was good compared to many, but to my fingers, there was something lacking. But since the keyboard was not mounted in a natural position, my impression of the touch may be incorrect. (Next visit, I'll ask for a better setup.)

Any suggestions would be appreciated, especially about alternatives, as I'd like to try as many as possible before making a decision.

For the exact same price, you can get the CP33, which has a heavier, and to me, a better, touch, but worse sounds and no built in speakers. I have one, but have it hooked to a computer running Pianoteq, so the sounds were not an issue as all I care about is the touch/action.

under $1500, the best Yamaha you could get is P155, unless you can go for $2000-3000 range for CLP330/340, which offer better GH3 action.

i'm going to get a P155 hopefully soon.

I would not forget the console model Yamaha YDP 223, which now can be found new at less than $ 1500. It is an older model but it has a great piano sound and good 20 + 20 W speakers.

No doubt a good piano but not as recent as the P155 and having just 64 note polophony compared to the 155's 128 and of course not meeting the requirement of the OP of being able to store vertically. Have to admit though i have a P155 and although you could certainly store it vertically somehow the idea of that makes me cringe.