I just picked up a Casio PX-310. So far, I love it.
I had tried the PX-300 a few months ago, and I was aghast at how much I liked the progressive action, since I never dreamed of buying a Casio and could picture the snickering looks of my bandmates. The grand piano sound was quite good, and the EPs were not bad, either. Then I found out it only weighed 28 lbs and cost $700! This struck me as an excellent package.
I decided to wait until the PX-310 came out, and I'm glad I did. The sounds are significantly better. In particular, the grand piano is now more accurate and responsive: in short, it's excellent. And it only weighs 26 lbs now! For those of you that care, they improved the built-in speakers.
In comparison, let me say that I consider the RD-700SX to be the most accurate digital piano out there, with its superb action and stunning grand piano. And its expandable. But it costs over $2000 and weighs over 50 lbs! For my purposes (playing rock and acid jazz) the extra weight and cost are not worth it. (Also worth mentioning: the RD-300SX has a terrible action and is over $1000, so it's not even in the running, even though it is also a lightweight board like the PX-310.)
In some ways, I like the PX-310 action even better than the RD-700SX. It has no springs, using only fluid to acheive its magic. This makes it very even and natural to play. You can really "dig in"; it reminds me of my Rhodes.
If you go to a store to test this keyboard, you need to plug it in and listen as you try the action. If you just walk up to it and play it when it is off, the action feels weird and mushy. But it "makes sense" when you hear it. Try it out and you will see what I mean.
The Rhodes (EP1) and the Wurly (60's EP) are quite playable, with some honk and bite to them. I would definitely use them at gigs. But it gets even more fun when I hook my Nord Electro to PX-310. The Nord's Rhode patch just comes alive! Its amazing how much richer my playing is with the weighted keys.
Some bits of advice:
* If you like to play the keyboard hard, set the keyboard touch to "Strong". This lets you play very delicate runs and then dig in for some fierce attack; the "thick" action really shines.
* The Clav is decent, nothing amazing but it will work in a pinch. I recommend turning off the DSP and see if you like the setting better (I did). It's a bassier, richer sound this way.
So yes, it's a Casio: wall-wart, built-in speakers, rhythm and auto-accompaniment, etc. But it's really a fantastic instrument, with a first-rate action and a great grand piano. It is absolutely the best deal out there right now. Go try one and you might be amazed.