I think the 3000-point tickets for coach travel in the NEC are a good way to go since they seem to provide the most value per point. A typical ticket in the NEC might be NYC to DC, which currently runs about $111 and up during peak travel time. If you redeem for six of these tickets, the implied value is nearly $700.

Another nice option is converting the miles to Continental Airlines (you'll have enough for a 20,000 mile reward ticket for RT travel anywhere within 1500 miles) or add 5K miles from elsewhere and you have enough for a 25K mile domestic RT ticket.

One word of caution is to stay away from the 10,000 point 1-hr advance upgrade coupons. These have pretty substantial blackout dates (Dec. 15- Jan. 2 is one huge blacked-out period, for example) and cannot be combined with a discount code since to upgrade your ticket, a new discount code must be entered. And unless you're upgrading on Acela from business to first (which is a pretty good value), you'll be redeeming 2500 points (the value of each of the four upgrades in the packet) for business accomodations that cost about $32 from NYC to DC ($20 from Philly to DC) and and are often sold-out less than 1 hour before voyages during peak travel times (meaning that you won't be able to use your upgrade coupon anyway and might be stuck in coach).