This is a free service, so it should be compared to free and low cost alerting (e.g. Google Alerts) and PE/VC funding profile (e.g. Crunchbase) services. Owler is well suited for competitive intelligence professionals, named account reps, and marketing professionals tracking company news (web mined company mentions and press releases) and social media (blogs, Video, YouTube). The alerts are high precision and tag for three key events (M&A, Funding, Exec Changes). It is the alerting and social media tools which are the key strength of the service.
The company claims two million profiles, but only has 60,000 with full address information. Content includes competitors, user polls, and funding / M&A data. Owler should be viewed as a free complement to other online company research tools, but it lacks the depth to replace subscription services. Missing content includes long business descriptions; financials and discrete sizing data; family tree linkage, and executive profiles (only the CEO is covered)
While they offer list building functionality, it is quite thin and non-downloadable. As such, I would not recommend Owler for sales and marketing prospecting at this point.
A unique feature is a set of company polls about the direction of the company and CEO performance. Unfortunately, the response rates are often too low to be statistically meaningful.