I don't have a graduated filter as Lee Filters are very expensive. Probably around $400 for a set of 3. I wouldn't use it often as I don't shoot many landscapes and cityscapes, so it wouldn't make sense. So currently, to answer your question - no I wouldn't get one. If I had disposable income I'd buy it in a heartbeat.
But one way around using graduated filters is shooting in HDR. Sure you're not getting the shot in camera - but you will get similar results.
I would however invest in a circular polarizing filter as the one I have is pretty beat up and you can't get the effects of a cpf in Photoshop / Lightroom.
Thanks for the comment.
Polorizers are the bomb. Have one, never comes off my 17-50 2.8