MacKeeper has got very bad press because of its aggressive method of using pop ups to advertise it. Professional reviews are positive but there is so much bad press about it in the blogs that my advice, too, would be to steer well clear of it. There are a number of other apps out there that do the same thing, are well respected and have a proven track record. I've had Macs for twelve years and I use and can recommend Clean My Mac, from MacPaw - a well-established software producer - for general routine cleaning and maintenance, and Drive Genius 3, from ProSoft - another well-established company - for more detailed and in-depth maintenance and hard drive cleaning and organising. Please note that this is personal experience and I do not own shares in either company!