According to Adobe, they are putting a priority on speeding up the the performance of Lightroom. The sluggish performance for some people using Lightroom has been a consistent concern for quite some time now.
Adobe on Lightroom Performance:
I would like to address concerns recently voiced by our community of customers around Lightroom performance, as improving performance is our current top priority. We have a history, starting with our first public beta, of working with our customers to address workflow and feature needs, and we’d like to take that same approach regarding your performance concerns. We already understand many of the current pain points around GPU, import performance, certain editing tasks and review workflows and are investing heavily in improving those areas. Over the past year we’ve added numerous enhancements to address your performance concerns but we understand we will have a lot of work to do to meet your expectations. If you have feedback or would like to work with the Lightroom team on your most pressing issues, please fill out this survey.
Adobe has apparently heard its customers and everyone should continue sending in concerns about Lightroom's performance issues.