If dropping 1.6 makes the core gameplay better, then it is worth dropping it in my eyes. As much as I feel for those who are at a disadvantage on their current computers, I care more about seeing the game work its best for the 95% who can update without issue.
Furthermore, optifine not being updated obviously has nothing to do with us. It is the fault of the optifine develeopers and could also be blamed on 1.7's needlessly over-complicated code. There are things we can do to alleviate this for our players (dual-support) but in the end I don't think it is our responsibility to help provide a mod that we don't develop when it comes at the cost of our own stability.