I'm going to go with highpower as well on this one.

Cleaning your cases:

1.) Makes it easier to see developing flaws in the brass early.

2.) Keeps your dies clean and prevents wear to the dies and scratches in the cases.

3.) Reduces sizing effort.

4.) Makes the cases look nice.

5.) Is fairly inexpensive.

I tumble all my cases before they are deprimed and sized. When I come home from the range I just dump the cases into my tumbler and turn it on. Because the cases weren't super nasty to begin with it usually takes just an hour or two to get them clean and sparkling. If you're looking for an inexpensive tumbler, go to MidwayUSA's sight (www.midwayusa.com) and search for the Frankfort Arsenal Tumbler. It's a base line, no frills unit that's big enough to clean 100 22-250, 50 .454 Casull, and 50 .45 Colt cases at the same time, and costs about $50.

For media I've found that the best, and cheapest, media one can get is a 50/50 mixture of pet store fine ground walnut hulls and the fine corncob bedding, treated with Iosso Brass Polish. The media costs a fraction of what it costs at a gun store (i.e. the Lyman tumbler media) and lasts three times as long. The 50/50 mix does an outstanding job of getting the cases sparkling clean and highly polished in little time.

Tumbling cases is worth the small bit of expense and trouble, IMO.

Mike