Pros
Can't think of any. Perhaps, if you're in favor of this, they're too hands-off.
Cons
I was hired for a position, and throughout my time with the company, not a single employee from the agency followed up to check in and see how things were going. I never expected them to until another agency hired me, and their work ethic compared to HKA is phenomenal.
If I ever reached out to them, it would take days for them to get back to me as well. I would reconsider going through HKA if you're job searching.