The key action movement in this model has been improved from previous years but all major (good) brands of cabinet model digital pianos have different key action mechanisms and overall do a pretty good job of recreating a decent piano keytouch once you get to the $1500-$2500+ price range. The AP620 key action feels responsive, and is overall a good moving key mechanism but is still not quite up to recreating an acoustic piano in terms of overall sound and sustain as compared to the new PX780. Although many of the higher priced digital pianos over $3000 are more advanced and sound great, there are digital pianos under $2000 that are more than adequate for an exciting piano playing experience including one of my favorites from the Kawai piano company, the CE220 (see below).
There is a chord accompaniment section for people (adults like this sometimes) who want to play with 1-finger or fingered chord styles without having to learn much or taking formal lessons. Also on board is a 16-track General MIDI recorder/player with built-in SD card storage which allows you to record 16 tracks of music one at a time and then play them back simultaneously. This can sometimes be a complex feature to use so it just depends on your musical goal and ability to use technology. There are also 360 drum patterns for rhythm training, which can be helpful if you don;t want to use a metronome, however connecting a good digital piano with a high speed USB connection to iPad can give you this and much more.
Oh and another thing; Casio has designed the Celviano AP620 keys to duplicate the look and feel of satin ivory piano keys. However the new PX850 keys have been upgraded further with even better ivory feel keys along with ebony feel black keys. The new synthetic ivory key material gives a better tactile, solid touch for the player's fingers (instead of regular plastic top keys), which is a very nice feature and one not found anywhere else in this price range.
Finally, you can connect the AP620 (and the new PX850) directly to a laptop/desktop computer using the piano's USB output for interactive piano lessons with great learning software (available from music software companies). And now you can also connect the Casio pianos to the Apple iPad with Casio's built-in "Class Compliant" USB CoreMIDI connection software for instant plug and play using the latest intuitive music apps on Apple's iPad for exciting educational and composition tools (left pics) including the famous Garage Band program. That is a very cool thing and motivational for piano students to use. There will always be people who find that another digital piano brand, model, or price range is better for them, but when you add up all of the features of this Casio AP620 piano, it is certainly worth considering although this piano came out in early 2010 and as I said earlier, it is a discontinued model now and it would be even better to consider the new 2013 PX850 with a substantially better key action and piano sound and then using an iPad to get the interactive technology. If you put the AP620 on a 1-10 scale comparing it as a "piano" to the new PX850, in my opinion the AP620 would be about a 5 or 6 as compared to a 9 or 10 for the other two...it's that much of a difference.