Casio CTK-900

Concerning software versions, since it has no "real" software running on it, there is no such thing as a version.
Presets sound ok through the internal speakers, but throught the output jack you can easil hear that they have way too much bass und lack highs and mids. Therefor they don't cut though in any sort of band situation.
Editing patches is easy. Especially using the multi band eq you can then get sounds that WILL be heard when there are other instruments present. However the given patch editor has one big problem: It can not read any patch files and also it does not change the keyboards parameters like editors usually do. So you'll have to program, save, upload and test. Useless.
The manual is very good, also including complete program change lists and stuff.

It comes with 32 note polyphony, which is by far too low. When playing with acompanyment you'll often have it loose the beat. Built in FX are pretty variable, though in some cases there are not enough parameters to edit. MIDI-wise you can pretty much program everything in the keyboard from outside, like changing the sounds of everything including the accompanyment. There's an onboard sequencer but because of the 32 note polyphony I haven't even tried it.
Memory banks can hold only 4 presets each. Not really enough for effective use.

In that price range you won't get any realistc sounding instruments. But still they do sound quite nice. I've been using it for a Prog Rock band (switching to Yamaha PSR 1500 now) and it did the job well. As I said you MUST use the equalizer alot though.
Effects are ok, but the distortions sound very cheap. Velocity responce is nice and adjustable.

Ok so far but I have the feeling that the most used keys (third octave) are starting to get slightly softer. Casio is pretty much more known as a "toy" company than a real maker of musical instruments, so of course there are drawbacks. Anyways nothing failed so far (5 months).

They took almost 2 weeks to respond to a very simple email question - only to tell me that what I was asking for is not possible with the keyboard. They did that by using only one short sentense, not even saying "sorry" or trying to get me an alternative solution. Bad.

It's an over-average instrument for its price range and can also do some basic band work. But after some time you will start to dislike some of the limitations and the very high need of editing the sounds. That's why I will make it the rehearsal room instrument now and get myself a new one for 3 times the prize to play gigs and do studio work.
It is worth what I paid (cause it was 33% off - given above is the usual prize), but I guess instead of buying it again I'd go and borrow me some mony for something that's at least double the prize.
Can be used nicely for some recording though.

I've just gotten my CTK-900, so I'm using entirely stock sounds that came with the keyboard. It's got a hell of a lot of features (especially for the price), so naturally it's complex to use. Reading the manual is a big help, though.

The only problem I've encountered so far is that I keep hitting the rhythm accompaniment keys by accident, but this can be solved by turning the rhythm volume all the way down.

I wish I could give a rating higher than 10 - more like 1000, actually! For a $200 keyboard, this not only has a large number of sounds but effects as well, each of which are highly customizable. There are numerous choruses, reverbs, delays, etc. and even rotary speaker simulations, each of which are customizable to the nth degree (once you figure out how to work them).

I originally bought this for use as a knock-around piano, but the drawbar organ feature is good enough that I'll certainly be recording with it. I particularly like how the keyboard saves effect and mode setting with the user presets. This way, when I call up my customized organ sounds I get my customized rotary speaker settings automatically.

The only major flaw is the lack of a line-out jack. There is a headphone jack which I use as a substitute. I don't use MIDI, but there are MIDI in and out ports and a jack for a sustain footswitch. It would be nice if it came with an AC adaptor (or even the 6 D-cell batteries it runs on), but these are cheap and easy to find.

Because you can customize each sound (including a multi-band EQ), you can make an infinite variety of sounds. The piano sounds are far nicer than Yamaha keys for the same price, though the synth sounds are so-so. The drawbar organ isn't going to fool a Hammond fanatic, but it is realistic enough to suggest some other vintage brand. Actually, it sounds better than my '70s Wurlitzer organ.

The onboard speakers are rather junky and are easily overloaded.

I've just recieved the keyboard, so it's a bit early to tell.

Never dealt with them.

I can't believe all the features that come for such a low price.