It depends which EQ3 it is and what you want to do with it, I don't have much experience with the new ones so I'll leave that for someone who knows.
As for the Focal Length and Aperture it's all in the name
150x750 means it's 150mm aperture and 750mm focal length (not sure what the "p" means?).
That seems like a pretty good deal for a reasonably 'fast' (good aperture/focal length ratio) refractor. The EQ3 probably wouldn't do too well for Astrophotography because the scope is close to the weight limit of the mount and the old ones didn't have sidereal tracking without upgrading the motors and controller (don't know about the new ones though). But it wouldn't be bad for visual use either.