The Casio Privia keyboards should also be considered due to decent action, modest cost, and low weight. I have the Privia 5X-5S, though I think the whole PX line has the same keybed so if you only want a keyboard you buy a less expensive model like the PX-350. Not claiming this a substitute for an actual piano, but I think it is a good value for the money. If you have a larger budget there are probably better keyboards, but as has been said by others, you should try out keyboards to see what you like (though in my experience high-end midi controllers are hard to find in music stores). Of course, another issue a Linux pianist faces is the limited options of good piano sounds (or any sounds). Luckily Pianoteq is available for linux and has gotten quite good, though not exactly cheap. I am also glad I picked up some SampleTekk gigasampler piano samples before they stopped selling them. TBO is my favorite, though Black Grand is also excellent. SampleTekk does sell SFZs of these, but they are not nearly as good as the gigasampler versions. The only decent open source piano is the Salamander grand. Quality of piano sound is mostly important for solo playing. In mix you can play almost anything and you won't notice the difference.