I think DomainTools’ Whois History tool is the most important domain tool I use, and it is only available to people with active DomainTools memberships. The History tool allows me to see who previously owned a domain name, and it can be used to make sure there hasn’t been any suspicious activity on a domain name.
To be blunt, I don’t know how anyone would be comfortable buying an expensive domain name in the aftermarket without doing a proper search using this particular history tool, since there don’t seem to be any competitors.
Earlier today, someone asked me to run a poll to see how many people here have DomainTools accounts, and I think that’s a pretty decent idea. Check out the poll below: