Mate I felt the same way, I bought my decks and thought fuck I've just wasted my money after a week or so... Just keep at it, its just a case of learning to seperate two tracks in your head. But it will come to you, it just takes time.
Anyway Vinyl is better to mix with. I dunno why it just feels like thats the way you should mix tunes, I'm not to keen on all this digital stuff, although I will probly invest in a cdj one day as I can play dubs, an maybe my tunes if I make some that way. But yeah nothing like the feel of a vinyl when you cueing up, an I enjoy beatmatching by ear, an not looking at a bpm counter. I supose it prefrence tho, although I find in dnb more dj's use vinyl than in genres such as house, techno, trance etc..