Very interesting questions
1.what do Registry cleaners do exactly? - well, I have Registry Mechanic but I'm not sure what exactly cleans it.
2.Do they create more problems or solve them? - I think that they create more problems, later I've setting conflicts of various programs
3.Or are companies who make these utilities just out here to make a buck? - undoubtedly!
4.Bottom line, do registry cleaners really work? - maybe some their parts work, the rest... are just a big question
5.And how are you to know if they are doing what they are suppose to do? - sometimes I check my windows registry but I think that there is no windows registry programs that clearly show you what they are suppose to do