Depends what you want to use the keyboard for as to whether you want weighted keys.
If you're a piano player, you'll want weighted keys.
If you're planning on learning piano, you'll want weighted keys.
If you want it to feel like a piano rather than a keyboard, you'll want weighted keys.
If you want the piano playing you record to sound more realistic, you'll want weighted keys, but only if you're used to playing with weighted keys already.
If you just want the keyboard to act as a midi controller and trigger others sounds, you probably don't need weighted keys.
Weighted keys are great if piano is the primary purpose but can actually get in the way of getting a realist sound/phrasing/articulation from other instruments. For example with things like strings and organ, you often want a smooth and perhaps fast transition between the keys. This can be difficult with weighted keys, especially if your not used to playing with them.
If I'm recoding strings or organ, I'll nearly always switch from my digital piano to the midi keyboard.
Hope this is useful.
Yodasdad.