The advantage of a rustic brick hearth is that it's BRICK! You can use pretty much any kind of abrasive to scrape off the top level of material and expose a new layer.

For example, you can use another brick to do that and see what kind of results you get. A sander with a heavy grit might do the job.

However, how you make it look less rustic is a more ambiguous question. You could do lots of things, such as filling in the grout lines and topping it with a layer of tile.

It shouldn't be rocket science, but you might have to do it over a time or two until you get a result with which you are happy.

TSP and a plastic brush will scrub most grime off. If there is any soot you can buy a fireplace cleaner at a local hearth shop that will clean up well too.

As far as dressing the brick up, take a look at the link below. It's something I had considered using to dress up a brick wall in my basement. I'm going to be using mineral paint instead but it might be just what you're looking for. There's lots of info on the website but I am not sure of cost.

Here is a link that might be useful: Dye Brick

Thanks to Seattlepioneer for the helpful advice. And thanks to nhyankee for the link to dye brick, which I will consider after I clean the brick and decide whether it needs further attention. You have both been very helpful. Best wishes for the holiday season and 2008.