Depends on the types of grains, how they were stored and what you like to drink. If it's a wide range from light to dark, then you'll get something between a Brown Ale and Robust Porter.
If the grains have been stored at room temperature or in an uncontrolled environment, they may end up tasting very stale, flat or even rancid. Poorly stored grain can harbor weevils.
Can I assume that the Extract is fresh? If it isn't, then it might not be worth it, either. Liquid Extract oxidizes and darkens after just a month or so of exposure to air. Canned Malt extract lasts longer, but not forever.
