Clearbit was a hole-in-one for us. We wanted a nice add-on solution for enriching leads that were going to salesforce. Clearbit delivered that, and more, with no BS.
I always get asked "how accurate is this data" and I have no idea how to answer. The data is accurate because if they don't have the data, it doesn't enrich. I also had about six months where I was sending empty field data from Marketo to SFDC with the default of [null] then after reading some support Clearbit docs, I realized the default overwrite for Clearbit MUST be [[unknown]]. Now, when fields are blank, Clearbit knows what it is allowed to overwrite. That was an eye-opener for me that my sales rep missed.
Use [[unknown]] as your blank state for empty fields from any third-party apps in SFDC and you'll see an amazing magic trick ;)
We're enriching so many leads and for first time as a marketer, I feel really smart with my customer data.