Has anyone out there hired a car in Warsaw through to Estonia??
If you plan to return the car to Warsaw there should be no problem. However dropping a car in another country often results in a costly drop charge. Be sure to ask the agency if that charge will apply.
If you return the car to Warsaw the only caution I would offer is to ask about unlimited mileage and about returning the car with petrol in the tank.
I have learned to read the contract carefully before you sign. Be sure it complies with your confirmation for the agent who rents the car on the web.
Don't let the agent rush you. If you don't get a copy in English, don't sign it.