My verdict: probably the best tool on the subject, at a premium price.
FullEnrich is great to put in sales' hands: it's simple and turnkey. Multi-source waterfall maximizes match rate automatically.
Very cool for enrichment, a bit expensive. If you do volume with APIs, it's much less attractive (you'll prefer cheaper specialized solutions).
What I like less: premium pricing can block tight budgets. And for technical profiles, building your own waterfall will be more economical.
My advice: for equipping a sales team with a top solution, it's the royal choice. For technical volume, look at alternatives like Enrow or build your own stack.