I bought this so I'd have an inexpensive and lightweight keyboard to take to gigs - for this, it's fine. I like the idea that if someone drops a pitcher of beer on it, there's no real tragedy. (The housing is soft plastic and you can easily bend it with a finger, but overall it doesn't seem terribly frail and I think it would take a pretty good whack to actually break it. The kind of whack that I wouldn't want to expose a nicer axe to, even if it held up.) In the places where I play live, "expressiveness" is not totally unimportant, but to be honest it's not a major factor.
I thought I might also be able to use this board in my home studio where I am more apt to care about dynamic subtleties (I'm also more likely to be playing a piano rather than some synth pad). For this, the Keystation is pretty much useless. The main problem is the inconsistency of velocity response from key to key - most of the keys have to be pounded pretty hard to reach the upper velocities, but a random few send out a high velocity with even a pretty light touch. I've never encountered anything like this before on even inexpensive keyboards; it seems crazy that it's a problem in 2005 when no one in the 1980's seemed to find it difficult. Again, if my main application had been something other than pounding the thing in bars, I'd have returned it on this basis.
Overall the action is a little more resistive than other synth-action keyboards I've played. I thought I would like this, but I find that when the resistance is a constant springiness, rather than a hammer action where the key "lays down" a bit after you have pressed it, then the extra resistance is just tiring. This is really subjective territory though.
Surely there's no way to comment on the reliability of a product that's only been around for a year or two? Ten years from now, we'll have an idea...
It's worth what I paid, but I'll eventually be looking for a keyboard that's useful in a really musical context. The whole controller market is a little strange to me right now as it seems dominated by two and three octave keyboards, I suppose for kids who don't really play but want to "trigger" things or do step entry. If you are a player, skip all this crap and spend a grand or two - you will have to buy a board with sounds even if you only intend to use it as a controller for your GigaStudio or whatever, but at this point I suspect it's the only way to get a reasonably responsive keyboard action under your fingers.