It is not "built and designed for scrypt GPU mining" any more than cgminer or bfgminer. It's a copy of them with ASIC support removed and a handful of optimizations added. The noteable ones have already been added to bfgminer.
If you want a scrypt-only, GPU-only miner (for some reason) go for it.
Edit: In fact, if you look at the SGMiner commits, they are pulling in code from BFGMiner including Luke's recent OpenCL fixes.
Edit #2: I have nothing against SGMiner btw. I just don't personally see a reason for a GPU-only, Scrypt only miner (SGMiner) just like I don't personally see a reason for a ASIC-only, SHA only miner (CGMiner). Especially if there aren't tangible benefits. I also don't think it's particularly productive to create yet another fork of a miner when there are already several in active development.
You contradict yourself, and none of your post make sense. I suppose I should have expected that from a LJR fanboy. How is SGMiner not "built and designed for scrypt GPU mining" when you yourself called it "a scrypt-only, GPU-only miner".
It's more than just CGMiner with the USB/FPGA/ASIC stuff removed. Yes, they stripped down all the SHA256 stuff, but also added much more, before LJR did. They fixed the R9 290 crashing-when-closing issue. They added the comma-separated-threads issue for different cards. They've since added multiple kernels. On my 280x, we use the Zuikkis scrypt kernel, which is different than the kernel we use for our 290. They've also added xIntensity, and rAwIntensity, both of which are awesome for tweaking. In short, it's the cgminer for scrypt that people always wanted.