We own two pianos at home but need a portable one for my child who travels for performances and competitions. We borrowed one Yamaha p-140 digital piano which we liked a lot about its weighted touch but felt a little burdened by the weight of the keyboard itself while traveling. Basically these are what we are looking for:
1. a 88-key portable one with weighted touches for serious practice on the go
2. since I myself improvise a lot, I also dream of having one keyboard that can print out whatever played, with some software build-in or attached, in to sheet music. I don't know whether this is an achievable goal, but if yes it would be just perfect.

We would really appreciate if you could give any suggestions and comments. Of course, if the 2nd function can not be found in any one that serves the 1st goal, we would at least get something for the main purpose of traveling practice.
Thanks a lot and enjoy 2010.

Well, you probably won't find a very good hammer action keyboard that's also very portable! Maybe the P-85, but the action on that one is much lighter than that of the P140. Still, I'd recommend that one.
The Casio PX 130 is quite light also, if I'm not mistaken, and has a much heavier action than the P-85.

For your second wish, the only option is to carry around a laptop, with some notation software and a printer.
You won't find that in any PORTABLE keyboard (I think the Yamaha DXG 630/YPG 635 has that, but it's huge).

The P155 has replaced the P140. But in terms of weight and touch is about the same. The sound is better. The problem is that weighted hammers have weights. These is no way around this. If you want a 12 pound piano look at the Yamaha NP30. But it lacks weighted hammer action keys but it's 12 pounds. You have to choose, can't have both. A wheeled case helps.

Of course you can print out sheet music for whatever you play. It's simple. Buy a small 13" size Apple Macbook. It comes with such software already installed and setup. You would be able to record your performance and then edit the notes and convert to music notation. With a computer you can also play sounds from a larger sample library. Other brands of computer and softare can work too, but you have to set it up the Mac is an out of the box solution to music production

Here is a guy showing how it works. This is just the basic functionality built into the Mac. You can buy better software later if you like
http://www.ehow.com/video_2372702_music-notation-garageband-tutorial.html

If you really want "portable" there are short unweighted keyboards as short as 25 keys wide. These can be used, battery powered with a notebook computer even in an airplane seat. Keyboard and note book would both fit inside cary-on sized luggage