[NationalCorporateData]

Different "lenders" for the CC stacking program may sometimes incorporate personal loans, which can obviously get the borrower more than if they went the credit card route alone.
Commission seems to vary from just 2-3 points to a full 50% share of up to 20 points being charged at closing.

Good
Access funds from multiple credit cards to get more capital than they normally would
Cash-out from cards without having to card advance fees
0% APR for 6-18 months

Bad
8-10+ credit hits in a short period, this doesn't get categorized as rate shopping so all hits remain
Personal funds being used to finance business activity, granted many businesses do start with personal funds anyway
The credit card companies may find out about each other if the program isn't executed correctly and cards can be cancelled
Long time to fund, typically the borrower has to go through credit inquiry removal and paydown existing debt or balances

Requirements
680 FICO
5 or less recent inquiries
35% utilization or less across all cards

Separate side note, Nav had a massive password breach recently so it might be good to avoid them for a while.

Edit: 680+ FICO, as abfunders below mentioned.