The CT-S1 is fantastic on every feature it has. The sounds are good, it feels very playable, the options on the front panel are rather well laid out... even the speakers really impressed me!
The only drawbacks to the CT-S1 lies in its auxiliary functions, and specifically their inaccessibility. Every secondary option is accessed by holding Function and pressing a key on the keyboard. Since nothing is labelled, everything becomes difficult : turning off the internal engine to use the keyboard as a MIDI controller, adjusting octaves... Though you may remember the most common ones after a while, I think the CT-S1 is just more fun if you want an instrument to sit in front of, press a button and play the piano instantly (or any other of the really nice integrated sounds).
In my setup, the CT-S1 is the "sample library instrument" whenever I want to record a piano loop or some strings. It fits the job super well, though at times I have wished for DIN or TRS MIDI rather than USB only.
In conclusion, the CT-S1 is a great instrument, and not just for beginners I think. It delivers high quality sounds, enjoyable playability (unless you are used to acoustic pianos, but it's not a quality issue), and the integrated speakers with their Surround function are a great bonus. Bring the price into the equation, and it seems like a must have for anyone who wants a practice instrument, inexpensive gigging machine, or musicians who are not primarily keys players and will not miss advanced features.
PS: the clean looks are not lost on me, and as someone who lives in one room, having beautiful instruments that inspire you to sit in front of them matters. It doesn't feel too cheap, but it looks more premium than it is, which is a pro to me. It brings warms and coziness to my music making space, and I love it for that as well as for its musical features.