I just picked up the Zenith DTT901 from Circuit City after reading about it on the conversion box thread over on the AVS forums. Many on there seem to agree that the 901 is among the best, if not the best, that qualifies for the government coupon. I couldn't be happier with it personally. The menu system is very well designed, the remote is good, and the reception/picture are excellent (for me anyway, in the Orlando metro area). With the gov coupon applied it was $20.
One note: Be sure to look for the DTT901 and not the DTT900. The 900 is the previous model and apparently had a few issues that were fixed in the 901. You may have to go to CC and check the shelf for it or call them directly, because the 900 is still the only model listed on their website. Radioshack carries it as well.