The Grand Canyon is absolutely stunning during the winter, and a great time to go.  The daylight is only about 5hrs. for most of the winter (10-3 about) so be prepared for shorter hikes on the trails that are open.

We have a lot at OhRanger.com on the Canyon in the winter, so be sure to read up on what's open, where to go and what to do.  About.com also has a wonderful resource if you click here:  http://gosw.about.com/od/arizonatravelguide/a/canyonwinter_2.htm

The answer to this basic question is... maybe! The weather is unpredictable, but the park itself will undoubtedly be magical.