Small turbo 4 configuration is dictated by need for fuel economy (versus a V6), if it's done well, no problem. IMHO turbo 4's and hybrids are critical in the mix to achieve high fleet MPG averages.
I have driven recent Mercedes small turbo 4's extensively and they deliver the right combination of power, refinement and fuel economy. I expect Lexus (being a premium automaker charging fairly high pricing) can deliver the same with it's turbo 4's.