I don't remember having this issue before but with lightroom 5.5, it sometimes takes 3-4 seconds between when i make an adjustment in the develop panel and seeing the result. In addition, zooming in to 100% of a raw file is extreeemeellly slow. It sometimes takes as much as 10 seconds. Im on a pretty fast computer too
6 Gb RAM
Huh seems to be gone but it was chugging a bit in the beginning.