I, too, used Registry Booster until last year. I never had any particular problems with it, but I was put off by the cost and the annoyance of being on Uniblue's mailing list. I did some research and came up with a short list of replacements to try. I wound up with IObit's Advanced System Care (ASC), which I subsequently upgraded to the Pro version to give me the automatic protection I was used to with Registry Booster, but was still $10 less expensive. IObit had previously caught my attention because of their free defrag utility which I installed on my daughter's PC (I use Diskeeper on my and my wife's PCs) after comparing it to Glary and Auslogics.
So far, ASC has proved at least as reliable as Registry Booster and also includes a junk files cleaner and spyware removal tool as well, both of which also run automatically. I've been running it long enough by now to recommend it, as I've noticed several others here have done as well.