These are mostly inputs from video game journalist Bertrand Amar and french website p-nintendo.com.
One of the biggest concern perhaps is how will the graphics fare on the larger screen. They say that unlike the shift from DSi to a DSiXL where the graphics got stretched, became more pixelated or in one word, worse, the 3DS XL does not make the graphics look degraded.
The 3D screen would also seem easier to the eyes, a possible sign of improvement on the 3D technology or it's really just better on a bigger screen. The improvement in size also gives spectators or people watching over your shoulder a better view of the 3D screen.
As most of us have seen, probably, the 3DS XL has a more curved design. It's been described as "much easier to hold" and the buttons and circle pad feels much better on your fingers probably because they are more "apart" in this sense.
With Nintendo trying to lower down the price, the 3DS XL will not come with a charger. The new 3DS model will come to Japan this August and will also be accompanied by a Circle Pad XL sometime this year. And these are facts by the way.