While the 3DS sales aren't bad, they're still a far shot from what the DS did. Selling 246,000 this week is good, but compared to the DS, it pales.
Look at it this way. After the DS Lite had launched worldwide - in mid 2006 - it never droped below 250,000 for the entire rest of the year. The lowest week was 267,000.
In 2007, the DS had one week in January where it only sold 238,000 due to supply issues, but other than that never dropped below 350,000 a single week for the entire year. (Or well, it sold 348,000 one week).
In 2008, the DS never had a week under 300,000.
In 2009, the DS only dropped under 300,000 a very few weeks, and never below 290,000.
In 2010, the DS dropped under 250,000 for a few weeks, both in May and September, but never under 220,000.
(In 2011, the DS dropped under 200,000 and stayed there for mostly the entire year.)
So, while the 3DS sales this week are nice in comparison to everything else, the DS managed to sell more than what the 3DS did this for 130 straight weeks - barring one supply shortage - and then matched the number for another 50 weeks. The 3DS is very unlikely to manage to stay at this level for many weeks, as it's boosted both by new hardware and a major game.
The 3DS is doing well in comparison to the direct competition, but rather rubbishly when compared to its predecessor. That's what the "doom and gloom" comes from.