There are a few places that sell discount, and don't advertise it as a sale price. BiMart has 901s for $50, Frys has 900s for $50 (no 901s yet). Those are regional stores, but other regions have similar things going on.
Now, is it worth waiting for a sale? If you are OTA with only analog tvs, and your networks are broadcasting digital now, it may be worth it to get one box at full price and start watching digital tv immediately. Once I converted one tv, nobody watched the unconverted tvs. After my first purchase, there were supply shortages and it was hard to find the second one. Hopefully things are better now that Zenith is apparently focusing entirely on the 901. A second trip to the store can eat up the price savings, so there may be no point in waiting if you know what you want and it is in stock.
Now if Dish comes out with the $40 box, it could put downward pressure on everyone else.