The Vivitek D552 has a maximum resolution of SVGA (800x600). That's 39% less resolution than a XGA (1024x768) projector, which is the most common resolution.
This projector's resolution (SVGA (800x600)) is actually the worst resolution amongst all multimedia projectors of this age and type.
A 1080p (1920x1080) native projector resolution is the best resolution across comparable types of projector.
Other projectors that have a resolution of SVGA (800x600) currently available which you might want to consider include the Infocus IN112A which has a better Rating.
If the resolution of this data projector is too low for you then you might want to consider the Infocus IN124 ($389.99) (XGA (1024x768)) which also has a higher Rating.