I say that lower end digital pianos may handicap you. For example, I just upgraded to a Yamaha P-95 from a Yamaha NP-30. The difference in touch was immeasurable. Also, Whenever I play on a grand at school, my playing improves dramatically. I think it would be because of the improved touch and sound of the grand piano. Keeping in mind that I learned how to play on a grand piano, and because of migration, I could no longer own it. There is just no comparison between my performance on grands, the P-95, and the NP-30.
I have not had a chance to try out any high-end digital pianos, so my scope is a bit limited. But my advice is, go for a good acoustic when starting to learn the piano. If you've developed proper technique and habits, and you're forced to, get a good digital, but only if you have to. The top two things, and the only things(assuming there are 88 keys), you should look at are the touch and the sound. If possible, compare with a grand piano and see which one is the most similar. Pedals might be necessary, but are usually part of the package. If the piano fullfills the above conditions, then I would get it.
Overall, I don't think that a digital piano in general will handicap you, in the sense that a digital, regardless of quality will cap you. If it's a high end, it shouldn't be to bad (I'm guessing). Entry level yamaha's will be ok if you have the right foundations. If you're starting from scratch, use an acoustic or a high end digital. As I said, I started on a grand, moved to digital, and play much better when I play on a grand, which is only occasionally.
Hope this answers some of your questions.