"Polished" would mean that the sand-cast surface has been smoothed. You don't really want a glass-smooth surface, but that's less important with port fuel injection (turbulence is necessary with 'wet' manifolds to keep the fuel droplets in suspension.)
If it were 'extrude honed,' I'd want a look at it myself. Extrude honing involves running a mild abrasive slurry through the manifold as if it were air - this not only polishes the surface, but it also helps to smooth out and round off projections that are in the way of airflow (since the theory goes that the slurry follows the same pattern as the air charge.)
"Porting" a manifold usually refers to "port-matching" - where the gasket is laid on the manifold face in its "as installed" position, and the manifold (and, usually, cylinder head) ports are opened up and tapered out to remove any "steps" at that point that would generate turbulence harmful to airflow.
"Port-matched" manifolds tend to want to stay with the heads they're matched to, since "port-matching" usually entails work on the cylinder head as well (you're matching the manifold port to the gasket port to the cylinder head port.) However, that just might mean that you'll only need to do a little work to the manifold to make it match up with your head.
Will it help? If the job was done well, it will probably help a bit. Airflow mods usually help - but they also tend to complement each other, and a number of small airflow mods can have a greater effect that just one big mod...
I'd probably get it, but I wouldn't use it raw for a project. I'd want to match it to my other parts first. Or, match my other parts to it.