I don't know a lot about all the cool stuff digital pianos enable you to do (and it is a lot), but I know enough to say that we are mighty pleased with the Roland Digital Piano (model HP-207) we acquired when we returned from India.
After the rather dismal experience we had trying to keep our old piano tuned and in condition in Bangalore, a piano that would never require tuning sounded appealing. That and the fact that digital pianos also allowed the pianist to experiment with varied instrument sounds propelled us toward a piano store that also sold digitals. Once there, the salesman promptly took us to the most expensive on the floor. We smashed his hopes - as gently as we could. Not only was it too expensive, it also had too many features that were not necessary for someone my son's age.
We saw a few more models on the floor, but the HP-207 seemed the most appropriate for our needs. The sound is awesome, the keys feel like and have the same weight as those of an acoustic piano. You can plug in headphones when you are practicing or lower the volume if you want to be quiet; you can play the drums or the guitar or the harpsichord (just a few of the more than 300 sounds promised by the manual); produce police car sounds or airplane sounds; you can record your own compositions; make use of the pre-recorded songs in the memory to learn new songs, etc., etc., etc. I'm sure there are a whole lot of other features my son has not discovered yet (the manual is hidden away safely for now).
We spent some time debating whether an instrument with all these features would be a distraction, but our son's teacher laid our doubts to rest. In his experience, having the other features (such as other instrument sounds or the ability to record a piece or a child's own composition and play back) on hand were valuable in the battle against boredom.
That observation has borne out. My son actually spends a lot more time at the piano than just practising his pieces - to fiddle with the settings, discover sounds, make up songs, etc. And it is a lot of fun to listen to all the different tunes wafting from a corner of the house.