Good - yes, it does what it is supposed to do.
worth the money? - no - there are free options - there are few pieces of software out there that don't have a freeware alternative, even if the alternatives are not as polished.
safe? No software is ever guaranteed to be safe on every machine.
Get a decent registry cleaner (RegCleanXP), temp cleaner (crapCleaner) and defragmenter (diskkeeper lite) and you have all that you need to keep your machine maintained.
Together with a decent AV program and a firewall to monitor trafic, you will be fine.