If u own both the 24-70 and the 105 you should consider why u bought both to begin with. Maybe u prefer one length over the other, maybe u like IS and of course the aperture. But u may also want to slow down before u take the plunge and think about the advantages of the doubly expensive version two. What on earth has Canon done to make this thing so much more expensive? Is it advertising bills u have to pay for? Or have they gone and performed a miracle in the desert? Every time they come out with something some people jump on the magic carpet and ride over to "L" world. But in the end it's your decision. The new version may be better and that's all u need to know.
could be because you were never totally happy with either lens.