We saw one at a car boot sale earlier this year when ds2 (just 7) knew he had £25 birthday money... And the dsi was only £20 with one of those game cards that has lots of games on. So couldn't reallyk out much of an argument up as he was spending his own money AND it was an incredible bargain.
Best £20 I ever spent. So much so that before hols we got ds1(8.5) one from the cash generator shop before hols, think that one was £40 but just a ds, no camera.
The games are much better than the ones they play on the iPod or phone, and the gadget is physically bigger, so they don't seem to forget where they put it, like they always do with the iPod which is dps with all his music on.
We use it to collect points or minutes for 'gadget time', they were brill going on hols as I was flying on my own with the kids this time, and they use their pocket money/spelling test money to choose games off eBay/amazon/from the game exchange.
If this is the one thing he wants for Xmas, then you don't need to get anything else, he will be made up to get one. Mine had also wanted them for a couple of years so they were thrilled to bits to finally get them.
In fact all they want this Xmas is a Marie game so it could be a very cheap year this year ha ha.