it's safe but don't know what type of extra items they may add if installed like browser addons and constant message to register if you do not purchase it

and with some of these types of apps, it will detect x number of errors and if not purchased full version, it may only fix a couple of what it finds and not all of them unless purchased.

Thanks for your info.

Have a read here: Uniblue Registry Booster - PCWorld Forums

You're better off with CCleaner.