I've used this plugin for a while and haven't experienced the issues other reviewers have mentioned.
I have tested site speed with it installed and active and got a 90% speed grade and an 84% YSlow grade. Uninstalled it, deleted cache, tried again. Got no difference results.
For me it has gave me a bit of piece of a mind as the changes it recommended when I first installed it made sense. And it has had no negative impact on other areas of my site.
So I would recommend it.