Alright, I splurged

I went for the YDP-181.
As far as touch, it is excellent. It's as close to a piano as you might want, except that the let-off part isn't felt. You can even miss a note if you don't press it fast enough, like a real piano. The key weight feels similar to an upright, almost. Sensitivity is quite good, you can play real pianissimo or fortissimo. I found pianissimo quite easier to do than on a real piano, so you might need some adjustment if you spend too much time on a DP :-p I don't know how many levels, I am sure I can measure that through MIDI.
The sound is pretty good, though there is still an "electronic" feel to it especially in the upper registers, and more if you enable "Damper Resonance". But that is in no way a show stopper. I think a DP is a great tool for practicing, you can record one hand and play with the other, or you can record one part of a two-piano piece and play the other part, etc. If you need better sound you can record to a USB flash drive and then replay the MIDI file with software like PianoTeq, TruePiano, or others.
All in all, great for apartment dwellers, or night time practice with earphones, and you can get very decent sound with piano software. For additional fun you can play organ or harpsichord.
My real worries are what if the instrument fails. Manufacturer warranty only goes for a year, after that you have to pay shipping to Yamaha should any repair be needed. Or, the store I got it from, Guitar Center, has an extended warranty on their own which covers shipping and other things. Still thinking about that. Then again, it's a Japanese product, and the Japanese are pretty good with quality, so let's hope for the best :-)
CG
Well yes, of course a DP always stays in tune
I was more thinking about wear and tear in the action, or problems with the electronics. At least your experience seems to be that they are reliable.
CG