This pretty much spells the end of humanity in it's current form. Evolution will be a thing of the past now. We will now choose our own path.
Evolution is inescapable. What this technology does is let us accelerate the process.
Yes I think it helps to accelerate evolution, whether that is in a 'good' or 'bad' direction is really open to debate. What I like is the enhanced management of evolution that this kind of technology will bring. Natural selection can be a harsh bitch. Childhood cancer? Sickle cell anemia? Autism (Couldn't resist) the list goes on...
Seriously though, why wouldn't you want to prevent some nastiness before it happens?
As a sidenote, I dislike the phenomenon of separating co-joined twins and the parents who insist on trying to save them when they are clearly a lost cause. It just seems like a deplorable waste of resources when it would have been much better to abort and have another go. I think if it happens twice in a row then you have bigger problems than having a rightful heir(s) to your little empire after you're gone. There was a story of a couple in the UK who had co-joined twins and decided not to abort and then there was a massive operation to separate them that failed while they were weeks old. I don't know for sure but I think the state picked up the bill for that one. You would hope the surgeons would have learned some useful and transferable skills from all that effort. So back to my point, problems like this need not be problems in future, and yes I don't think everything will be biscuits and tea either...