Yes, many travellers do this. If you have a passport that does not require a visa to enter Japan, just fill in the landing/departure immigration cards distributed before landing at NRT and write "transit - 3 hours" in the "length of stay" or "purpose of visit" fields. Then go through immigration and customs as usual. You should not encounter any problems as I've done that many times as a revenue passenger and the immigration official just politely nods and smiles and waves you through.

If you have a passport that does require a visa to enter Japan and you don't have one, I believe you can get a "shore pass" which allows you to stay for 72 hours for the purpose of transit. There are forms available in the immigration area.

Once outside customs and in the arrival hall, there is a pretty comprehensive shopping/dining area just adjacent to the Terminal 1 check-in area (there is a similar on in Terminal 2). There are about a dozen restaurants. Check out the Observation Deck on Level 5 which offers good views of the Terminal 1 apron and Runway 16R/34L which is the runway directly next to Terminal 1.

I am not sure you have quite enough time to venture out to Narita city which is only one train stop away, but if you happen to arrive early at NRT due to weak headwinds, you could go to the city for half an hour or so. The ride takes about 10-15 minutes. Narita city is a nice little quaint town with a temple.

You will find it refreshing that security lines at NRT aren't usually very long. Plan on about 15 minutes max to get through security and back though immigration. However, allow an extra 5-10 minutes to get to the new UA gate areas which are now at the end of the new pier instead of the rotunda which was more convenient.

Of course, this leaves little time to explore the RCC and the famous beer machine, or the showers!