There are big jumps in prices in digital pianos.
For the 100-300 price range, you get basic small keyboard with unweighted plastic feeling keys.
For the 300-600 price range you can get one like that Yamaha - it has 'light-weighted' keys, which has better feeling (and more realistic) keys. But it still has only 66 keys, not the full 88 of a piano. It also should have a higher polyphony (sp?), meaning that you can press more keys at the same time and still get a real sound.
For the 700-2000 price range you can get a full sized (88key), heavy weighted digital piano, with a really polyphony (I think 16). It's close enough to a real one. But for that price you might as well get a real piano used, if you don't mind the yearly tuning payments.
I have had a full size Roland FP-3 heavy weighted digital piano for about 5 years. I got it for around $900 . It sounds great and feels good. I also have an old upright piano I bought used about 15 yrs ago. It's been untuned for a few years, but the keys feel better than the digital piano and feel smoother too.
I suggest going into a local Guitar Center or music shop with keyboard displays and testing them out, and see which ones feel better. Find out what is more important- price or better weighted/feeling keys. But since it's a gift for someone else, that might be pretty hard to do.
