Well the price was sure as hell right! I say you say you have a too low 40 meter dipole. What is too low?
If properly installed the R-8 may give you an advantage when it comes to DX on 40 meters. Again it depends on how low that dipole is.
My 40 meter dipole is only up about 29 feet at the apex and I do ok with it. Sure not as good as I would if it was at 60 feet. But I can work DX on it and it works well for rag chewing within a 500 mile radius of my location.
As K7SGJ noted the noise level may be higher on the vertical. A lot of your local QRN will be more noticeable on the vertical.