Casio CT-S500

Great fun top board and couch piano. Bought a year ago and did ~30 pop gigs with it. Pitch bend and cutoff resonance controls make this more useable than my nord electro for a second board.
Decent speakers and battery power make this extra fun, I like the really tough light plastic body.
Also great ‘wedding band’ top board. Great for clavs, strings brass wurlis synths, decent organs and Rhodes. I never use piano patch but it’s decent. Loads of editable effects.
Only reason I took a star off is the patch storing menu.
You can’t store a name of a patch which makes recalling old patches a drag. Could be easily fixed in a firmware update but I won’t hold my breath. massive price drop since I bought it, that’s a bargain.
I have since upgraded to ck61 which I also recommend, even at 3x the price

Casio market this as a performance keyboard and in some sense this is correct. It focusses on having a decent set of performance sounds which can be adjusted with the DSP. The pre made tones do repeat a fair bit, with just different default DSP settings (you can't see what they are) which then can be replaced with your own, but you'll recognise repeated basic tones. You can get passable organ with fast/slow Leslie changes (via a knob).

I bought it as a super lightweight board for situations where I didn't want to take a pro keyboard and amplification with me but did not want to pay a fortune. The other contender would have been the Roland Go Keys 5 as I did want 1/4 jack outputs for a case where I might want to use it at a pinch for a gig.

The main thing I don't like about it are that they key travel depth is very shallow. I did have some fun with the basic arranger stuff such as backing beats (less so chords as I usually switch these off).

I would say that this keyboard would be a good keyboard for teenagers that were playing in bands but could not afford a more expensive board, or as a 2nd board which is easier to take to friends houses etc. The shallow key depth might be a problem if played hard when rocking out perhaps.

I would not recommend this board for somebody who wanted to learn piano, nor is it for people interested in electronic music as it is setup more for being in a band than anything. As a secondary board to a Piano elsewhere to sit in a bedroom to aid composition etc, if not going down the computer route at first it would work.

For a younger child, I think this may work as being a more serious keyboard as whilst the keys feel toy like, the keyboard itself as a whole is setup more for performance. If a parent was musical or the child was more interested in music vs goofing about it would work. It may however be a bit boring or overwhelming for a younger child vs a board designed for children.

If having at home and not gigging and not being bothered about 1/4 jacks, then the alternative that appears more serious would be the Roland Go Keys:3 which doesn't cost much more.

Overall it is quite a niche product. It's not a pro product, obviously given the price, but it is much better than cheap rubbish from Amazon.

I'm very happy with it, though it is worth knowing the use case for this board. I see it as a jamming in the park type keyboard basically, where I wouldn't be left out as a keys player compared to people with guitars.