There’s a new taxi fare estimator/Google maps mashup at the Washington Post site. You can enter an address or click a point on a map for origin and destination, and see how the fare would compare between the old zone system and the new meter plan. It also estimates the extra cost from traffic, giving a range so you can get a sense for how much more a trip might cost in heavy traffic. Most trips seem to be lower under meters, now that the base fare has been lowered. And this calculation doesn’t even account for no longer paying extra for extra passengers.
One complaint about the zone system was that many people were confused about what to do if a trip started or ended on a zone boundary. Once, before moving to DC, I took a taxi from U St (a zone boundary) and the cabbie insisted that because he picked us up on the north side of U Street, the ride was two zones. In fact, the law says that starting or ending on a boundary street counts as being in the zone closer to the other end (i.e. the point is in whichever zone makes the fare less). Unfortunately, the Post mashup gets this wrong… but so does the zone calculator posted on the DC government site. The Post mashup also doesn’t cap the fare at $18.90, which is in the new regulations.